Stairlift surveying, designing and / or installation

Abstract

A system and method of surveying an area for a stairlift comprising using measurement device 601 having a lidar sensor to collect data indicative of physical dimensions of the area. The system and met

Description

TECHNICAL FIELD The present disclosure relates to a method and apparatus for surveying an area for a stairlift. The present disclosure relates to a method and system for designing a stairlift for an area. The present disclosure relates to a method and system of installing a stairlift in an area. BACKGROUND A stairlift is a mobility aid that assists users in traversing an incline. A stairlift typically comprises a platform or chair, a rail, and a drive unit. The drive unit translates the platform or chair along the rail. When a stairlift is installed in an area, the rail must be configured to suit the area that it is installed in. A survey of the area to gain knowledge of its physical dimensions is a typical first step in designing a stairlift for the area. The survey may involve measuring the physical dimensions of the area. For instance, inclines in man-made structures are rarely equivalent even if intended to be of the same specification due to imprecision and variability in the building of said incline. A survey must therefore be conducted at each area in which a stairlift is intended to be installed. Presently, stairlift surveys are conducted either manually, using tools such as a tape measure and spirit level - resulting in hand drawn and noted data - or via one of several photogrammetry methods. Both manual and photogrammetry methods may require a relatively high level of skill to be performed adequately and therefore may typically be conducted by an operative specifically employed as a surveyor. A survey must accurately represent an area in order to allow a stairlift to be designed for the area. Inaccuracies in the survey may result in a stairlift being designed that is unsuitable for installation in the area. Often, the initial stages of a stairlift installation may include at least two home visits, e.g. a first visit when the site and user are assessed for suitability, and a second visit when accurate dimensions of the staircase and surrounding area are taken. These visits may add cost and time into the sales, production and installation of the product. Both manual and photogrammetry methods are susceptible to human error at both gathering and interpreting stages and can also result in questioning of data and re-visits which increases cost and time. SUMMARY OF INVENTION A first aspect provides a method of surveying an area for a stairlift, the method comprising: using a measurement device comprising one or more measurement sensors to collect measurement data that is indicative of one or more physical dimensions of the area; wherein the one or more measurement sensors include a Lidar sensor. Lidar is an acronym for light detection and ranging. Lidar works by sending laser light from a source, having it reflect from objects in an area and then detecting the reflected light. The time the light takes to travel from the source and back to the receiver can be used to measure the distance between the Lidar transmitter / receiver and an object in the area. At least part of the measurement device may be part of a computing device. At least part of the measurement device may be part of a handheld device. At least part of the handheld device may be a programmable handheld device. The handheld device may be a mobile or tablet computing device. In implementations, the handheld device may be an iPad®. The measurement device may be comprised within a single housing, or the measurement device may not be comprised within a single housing. The measurement data may include at least a point cloud. The measurement data may be in the form of a point cloud. The point cloud may contain coordinates indicating locations where the measurement sensors have determined that there is something solid. The measurement data may be indicative of one or more surfaces in the area. The measurement data may be indicative of the relative positions and / or spatial extent of at least two surfaces in the area. The measurement sensors may further comprise an infrared sensor and / or an image sensor. A mixture of different types of sensors may permit the collection of more accurate and / or detailed measurement data than a single type of sensor on its own. For example, data collected by the or an image sensor may be combined with data collected by the Lidar sensor. This may allow more accurate and / or detailed measurement data to be collected than using the Lidar sensor alone. The measurement device may comprise a camera. For example, the camera may be configured to take one or more pictures of the area before, during, and / or after the measurement sensor(s)’ collection of measurement data. The camera may be configured to take one or more videos of the area before, during, and / or after the measurement sensor(s)’ collection of measurement data. In implementations, the picture(s) and / or video(s) may be used to provide texture to any models that are subsequently created based on the collected measurement data. The picture(s) and / or video(s) may be used to check the veracity of the measurement data collected by the measurement device. The picture(s) and / or video(s) may be compared to any model representations created based on the collected measurement data to check the veracity of said model representations. The picture(s) and / or video(s) may be used to assist in the creation of a model representation of the area. The measurement device may comprise one or more usage sensors. The one or more usage sensors may be configured to collect usage data that is indicative of how the measurement device is being used while it is collecting measurement data. The usage data may be indicative of a position and / or an orientation and / or a movement of the measurement device or of at least one of the measurement sensors while it is being used to obtain the measurement data. When the measurement device is comprised within a single housing, the usage data may pertain to the measurement device as a whole by virtue of the measurement device being a single body. When the measurement device is not comprised within a single housing, the usage data may pertain to one or more of the measurement sensors, for example, the Lidar sensor. The one or more usage sensors may include an accelerometer and / or an inclinometer and / or a gyroscope and / or other sensors suitable for measuring a position and / or an orientation and / or a movement of the measurement device. The usage sensors are responsible for obtaining the usage data. The one or more usage sensors may obtain usage data while the measurement device is being used to obtain the measurement data. The usage data obtained may be indicative of the instantaneous position of the measurement device relative to a fixed point. The fixed point may be the starting point at which the measurement device began to be used to collect measurement data. The usage data obtained may be indicative of the instantaneous orientation of the measurement device. The usage data obtained may be indicative of the instantaneous position of the measurement device. The usage data obtained may be indicative of the instantaneous velocity of the measurement device. The usage data obtained may be indicative of the instantaneous acceleration of the measurement device. The instantaneous acceleration may be an instantaneous linear acceleration or an instantaneous angular acceleration of the measurement device. The usage data may be indicative of a closest and / or a furthest distance between the measurement device and a surface of the area being surveyed. The usage data obtained may be indicative of the average orientation and / or position and / or velocity and / or acceleration of the measurement device over a period of time. The usage data obtained may be indicative of a rate of change of the orientation of the measurement device. The usage data, in particular the position and orientation of the measurement device when the measurement device is comprised in a single housing, or the Lidar sensor when the measurement device is not comprised in a single housing, may be combined with the measurement data collected by the Lidar sensor. Knowing the orientation of the measurement device or Lidar sensor may allow the direction in which the Lidar sensor emits photons to be determined. Knowing the position of the measurement device relative to a fixed point may allow a relative position of the Lidar sensor to be known. Knowing the position and orientation of the Lidar sensor relative to its starting point when measurement began while using the Lidar sensor may allow a 3D map of surfaces in the area to be determined. The measurement device may analyse the usage data by comparing the usage data to threshold values. The threshold values may include any one or more of a minimum and / or a maximum orientation angle of the measurement device, boundaries for the position of the measurement device, a minimum / maximum velocity of the measurement device, a minimum and / or a maximum acceleration of the measurement device, a minimum distance between the measurement device and the boundary of the area being measured, and / or a maximum distance between the measurement device and the boundary of the area being measured. Generally, the threshold values may be threshold values for anything measured as usage data by the usage sensor(s). The measurement device may be configured to indicate to a user the correctness of their operation of the measurement device based on the analysis of the usage data performed by the measurement device. The measurement device may relay a visual and / or audible signal to the user that is indicative of the correctness of their operation of the measurement device. The measurement device may be configured to give the user real-time feedback on the correctness of their operation of the measurement device based on the analysis of the usage data performed by the measurement device. The measurement device may comprise a communication interface. The communication interface may be configured to enable the measurement device to communicate with a remote server and / or a device remote from the measurement device. The communication interface may enable the measurement device to communicate, for example, via a mobile network, Bluetooth® and / or Wi-Fi. The measurement device may comprise one or more indicating devices. The indicating device(s) may comprise a visual and / or an aural and / or a haptic indicating device. The indicating device(s) may comprise a screen and / or a speaker and / or a vibratory device. The indicating device(s) may be configured to allow the measurement device to communicate with a user. The measurement device may comprise one or more input devices. The input device(s) may comprise one or more buttons and / or one or more touchscreens and / or one or more microphones. The input device(s) may be configured to allow the user to communicate with the measurement device. The measurement device may comprise a processor. The processor may be configured to execute instructions. The processor may include one or more processing units for executing instructions. The processor may be operatively coupled to the measurement sensor(s), the usage sensor(s) (if present), the communication interface (if present), the indicating device(s) (if present), and / or the input device(s) (if present) when any of them are comprised in the measurement device. The processor may be configured to interpret user inputs received via the input device(s) and to initiate the collection of measurement data. The processor may be configured to analyse the usage data collected by the usage sensor(s). The processor may be configured to control what is displayed / indicated by the indicating device(s). The processor may be configured to interpret data from the Lidar sensor(s) and create, for example, a point cloud, e.g. a 3D point cloud. The processor may be configured to combine data from the Lidar sensor(s) and the usage sensor(s) (if present) and / or the image sensor (if present) and / or any other measurement sensor(s) (if present), to create, for example, a point cloud. The method may further comprise converting measurement data into a human-readable format. The measurement device may be configured to convert the measurement data into a human-readable format. The processor may be configured to convert the measurement data into a human-readable format such as a mesh. A mesh may be understood in this application to mean a 3D representation comprising a collection of faces, edges, and vertices that define a 3D shape or structure. Converting the measurement data into a human-readable format may comprise converting the measurement data into a mesh and displaying a representation of the mesh to a user. The measurement device may comprise, or be configured to be connected to, a display screen that is configured to display the mesh to a user. In implementations, in which the measurement device comprises a screen and a camera, the measurement device may be configured to display a real-time feed from the camera on the display screen. The measurement device may be configured to produce a visual augmented reality (AR) experience for a user. The visual augmented reality experience may comprise, or consist of, a video feed from the camera and the mesh. The method may further comprise displaying a mesh or other data representation to a user and, optionally, the user accepting or rejecting the collected measurement data based on the mesh or other data representation displayed to them. A second aspect discloses a method of designing a stairlift for an area, the method comprising: surveying an area for a stairlift using the method of the first aspect; converting the measurement data into a model representation of the area; and designing a stairlift for the area using the model representation of the area. The method may comprise converting the measurement data into a model representation of the area and designing a stairlift for the area using the model representation of the area only when a user accepts the collected measurement data based on a mesh or other data representation displayed to them. Converting the measurement data into a model representation of the area may comprise converting the measurement data into one or more computer aided design (CAD) parts, and then processing the CAD parts into a model representation of the area. A CAD part may be a portion of the area represented as a 3D solid or surface that can be used for CAD purposes. Converting the measurement data into a model representation of the area may comprise transmitting the measurement data to a remote server. Converting the measurement data into one or more CAD parts may occur at or in the remote server. Converting the measurement data into a model representation of the area may comprise the remote server transmitting the one or more CAD parts to another device or workstation. The device or workstation may be configured to process the CAD parts into a model representation of the area. An operative may operate the device or workstation. Designing a stairlift for the area may comprise the or an operative designing the stairlift for the area. A third aspect provides a method of installing a stairlift in an area, the method comprising: designing a stairlift for the area using the method of the second aspect; and installing the stairlift at the area. The method may further comprise manufacturing one or more of the components necessary to implement the designed stairlift. The method may further comprise delivering one or more of the components necessary to implement the designed stairlift before installing the stairlift at the area. A fourth aspect provides a measurement device for surveying an area for a stairlift, the measurement device comprising: one or more measurement sensors, including a Lidar sensor, configured to collect measurement data that is indicative of one or more physical dimensions of the area. At least part of the measurement device may be part of a computing device. At least part of the measurement device may be part of a handheld device. At least part of the handheld device may be a programmable handheld device. The handheld device may be a mobile or tablet computing device. In implementations, the handheld device may be an iPad®. The measurement device may be comprised within a single housing, or the measurement device may not be comprised within a single housing. The measurement data may include at least a point cloud. The measurement data may be in the form of a point cloud. The point cloud may contain coordinates indicating locations where the measurement sensors have determined that there is something solid. The measurement data may be indicative of one or more surfaces in the area. The measurement data may be indicative of the relative positions and / or spatial extent of at least two surfaces in the area. The measurement sensors may further comprise an infrared sensor and / or an image sensor. A mixture of different types of sensors may permit the collection of more accurate and / or detailed measurement data than a single type of sensor on its own. For example, data collected by the or an image sensor may be combined with data collected by the Lidar sensor. This may allow more accurate and / or detailed measurement data to be collected than using the Lidar sensor alone. The measurement sensors may comprise a camera. For example, the camera may be configured to take one or more pictures of the area before, during, and / or after the measurement sensor(s)’ collection of measurement data. The camera may be configured to take one or more videos of the area before, during, and / or after the measurement sensor(s)’ collection of measurement data. In implementations, the picture(s) and / or video(s) may be used to provide texture to any models that are subsequently created based on the collected measurement data. The picture(s) and / or video(s) may be used to check the veracity of the measurement data collected by the measurement device. The picture(s) and / or video(s) may be compared to any model representations created based on the collected measurement data to check the veracity of said model representations. The picture(s) and / or video(s) may be used to assist in the creation of a model representation of the area. The measurement device may comprise one or more usage sensors. The one or more usage sensors may be configured to collect usage data that is indicative of how the measurement device is being used while it is collecting measurement data. The usage data may be indicative of a position and / or an orientation and / or a movement of the measurement device or of at least one of the measurement sensors while it is being used to obtain the measurement data. The one or more usage sensors may include an accelerometer and / or an inclinometer and / or a gyroscope and / or other sensors suitable for measuring a position and / or an orientation and / or a movement of the measurement device or of at least one of the measurement sensors. The usage sensors are responsible for obtaining the usage data. The one or more usage sensors may obtain usage data while the measurement device is being used to obtain the measurement data. When the measurement device is comprised within a single housing, the usage data may pertain to the measurement device as a whole by virtue of the measurement device being a single body. When the measurement device is not comprised within a single housing, the usage data may pertain to one or more of the measurement sensors. The usage data obtained may be indicative of the instantaneous position of the measurement device relative to a fixed point. The fixed point may be the starting point at which the measurement device began to be used to collect measurement data. The usage data obtained may be indicative of the instantaneous orientation of the measurement device. The usage data obtained may be indicative of the instantaneous position of the measurement device. The usage data obtained may be indicative of the instantaneous velocity of the measurement device. The usage data obtained may be indicative of the instantaneous acceleration of the measurement device. The instantaneous acceleration may be an instantaneous linear acceleration or an instantaneous angular acceleration of the measurement device. The usage data obtained may be indicative of the average orientation and / or position and / or velocity and / or acceleration of the measurement device over a period of time. The usage data obtained may be indicative of a rate of change of the orientation of the measurement device. The usage data may be indicative of a closest and / or a furthest distance between the measurement device and a surface of the area being measured. The usage data, in particular the position and orientation of the measurement device when the measurement device is comprised in a single housing, or the Lidar sensor when the measurement device is not comprised in a single housing, may be combined with the measurement data collected by the Lidar sensor. Knowing the orientation of the measurement device or Lidar sensor may allow the direction in which the Lidar sensor emits photons to be determined. Knowing the position of the measurement device relative to a fixed point may allow a relative position of the Lidar sensor to be determined. Knowing the position and orientation of the Lidar sensor relative to its starting point when measurement began while using the Lidar sensor may allow a 3D map of surfaces in the area to be determined. The measurement device may analyse the usage data by comparing the usage data to threshold values. The threshold values may include any one or more of a minimum and / or a maximum orientation of the measurement device, boundaries for the position of the measurement device, a minimum and / or a maximum velocity of the measurement device, a minimum and / or a maximum acceleration of the measurement device, a minimum distance between the measurement device and the boundary of the area being measured, and / or a maximum distance between the measurement device and the boundary of the area being measured. Generally, the threshold value(s) may be threshold value(s) for anything measured as usage data by the usage sensor(s). The measurement device may be configured to indicate to a user the correctness of their operation of the measurement device based on the analysis of the usage data performed by the measurement device. The measurement device may relay a visual and / or audible signal to the user that is indicative of the correctness of their operation of the measurement device. The measurement device may be configured to give the user real-time feedback on the correctness of their operation of the measurement device based on the analysis of the usage data performed by the measurement device. The measurement device may comprise a communication interface. The communication interface may be configured to enable the measurement device to communicate with a remote server and / or a device remote from the measurement device. The communication interface may enable the measurement device to communicate, for example, via a mobile network, Bluetooth® and / or Wi-Fi. The measurement device may comprise one or more indicating devices. The indicating device(s) may comprise a visual and / or an aural and / or a haptic indicating device. The indicating devices may comprise a screen and / or a speaker and / or a vibratory device. The indicating device(s) may be configured to allow the measurement device to communicate with a user. The measurement device may comprise one or more input devices. The input device(s) may comprise one or more buttons and / or one or more touchscreens and / or one or more microphones. The input device(s) may be configured to allow the user to communicate with the measurement device. The measurement device may comprise a processor. The processor may be configured to execute instructions. The processor may include one or more processing units for executing instructions. The processor may be operatively coupled to the measurement sensor(s), the usage sensor(s) (if present), the communication interface (if present), the indicating device(s) (if present), and / or the input device(s) (if present) when any of them are comprised in the measurement device. The processor may be configured to interpret user inputs received via the input device(s) and to initiate the collection of measurement data. The processor may be configured to analyse the usage data collected by the usage sensor(s). The processor may be configured to control what is displayed / indicated by the indicating device(s). The processor may be configured to interpret data from the Lidar sensor(s) and create, for example, a 3D point cloud. The processor may be configured to combine data from the Lidar sensor(s) and the usage sensor(s) (if present) and / or the image sensor (if present) and / or any other measurement sensor(s) (if present), to create, for example, a 3D point cloud. The processor may be configured to convert the measurement data into a human-readable format such as a mesh. In implementation, in which the measurement device comprises a camera and comprises, or is configured to be connected to, a display screen, the measurement device may be configured to display a real-time feed from the camera on the display screen. The measurement device may be configured to produce a visual augmented reality experience for a user. The visual augmented reality experience may comprise, or consist of, a video feed from the camera and the mesh. The measurement device may be configured to display the mesh or other data representation to a user and, optionally, to allow the user to accept or reject the collected measurement data based on the mesh or other data representation displayed to them. The measurement device may be configured to transmit the measurement data and / or the mesh to a remote server and / or an operative. A fifth aspect provides a system for surveying an area for a stairlift comprising: a measurement device according to the fourth aspect; and a server remote from the measurement device in communication with the measurement device; wherein the measurement device is configured to transmit measurement data to the server. The server and the measurement device may be in communication via a mobile network. The server and measurement device may be in communication via any suitable communication means. The server may be operable to convert the measurement data into one or more computer-aided design (CAD) parts. A CAD part may be a portion of the area represented as a 3D solid or surface that can be used for CAD purposes. The server may be operable to process the CAD parts into a model representation of the area. The model representation of the area may comprise, or consist of, a 3D surfaced representation of the area that is suitable for use in designing on. A sixth aspect provides a system for designing a stairlift for an area comprising: a system for surveying an area for a stairlift according to the fifth aspect; wherein a remote device or workstation is in operable communication with the server. The server may transmit one or more CAD parts to the remote device or workstation. The remoted device or workstation may be configured to process the CAD parts into a model representation of the area. The server may transmit, in use, a model representation of the area to the remote device or workstation. An operative working at the remote device or workstation may design a stairlift for the area using the model representation of the area. Designing the stairlift may be done using a CAD program on a computing device. Designing the stairlift may include cost constraints that need to be satisfied such that the cost of installing the designed stairlift falls at or below a cost threshold. The cost threshold may be determined by a budget decided upon by an owner or occupier, or someone acting on behalf of the owner or occupier, of the area in which a stairlift is to be installed. Designing the stairlift may include producing an estimate of the cost of installing the stairlift. In some examples, once a stairlift has been designed for the area, a final product model representation may be created that shows a model of how the installed stairlift will appear in the area. This final product model may be communicated to the measuring device or a display screen operably connected thereto and displayed to an owner or occupier, or someone acting on behalf of the owner or occupier, of the area being surveyed, in order to allow them, for example, to approve or disapprove the design. The final product model may be communicated from the remote device or workstation to the server, and then from the server to the measurement device. Alternatively, the final product model may be communicated directly from the remote device or workstation to the measurement device. Such a communication may be done using any suitable means of communication or data transfer, including, for example, via a mobile phone network, Bluetooth® or Wi-Fi. The skilled person will appreciate that except where mutually exclusive, a feature or parameter described in relation to any one of the above aspects may be applied to any other aspect. Furthermore, except where mutually exclusive, any feature or parameter described herein may be applied to any aspect and / or combined with any other feature or parameter described herein. BRIEF DESCRIPTION OF THE DRAWINGS Examples of the present disclosure will be described, purely by way of example, with reference to the accompanying drawings in which: Figure 1 shows schematically an example of a measurement device for surveying an area for a stairlift; Figure 2 shows a flow diagram for a method of collecting measurement data when surveying an area for a stairlift; Figures 3a, 3b, and 3c show screenshots of a display of a measurement device giving feedback to a user while it is being used to collect measurement data when surveying an area for a stairlift; Figure 4 shows a flow diagram for a method of surveying an area for a stairlift, designing a stairlift for the area, and installing a stairlift in the area; Figure 5a shows a frontal view of a measurement device for surveying an area for a stairlift; Figure 5b shows a rear view of a measurement device for surveying an area for a stairlift; Figure 6a shows schematically how a measurement device may be used to survey an area for a stairlift; and Figure 6b shows schematically how a measurement device may be used to survey an area for a stairlift. DETAILED DESCRIPTION Figure 1 shows schematically an example of a measurement device 100 for surveying an area for a stairlift. The measurement device 100 in this example is part of a computing device. The measurement device 100 may be part of, e.g. housed at least partially within, a handheld computing device, such as a mobile phone or tablet computing device. In some examples, the measurement device 100 may be comprised within a single housing, e.g., a single tablet computing device comprising all features of the measurement device 100. In some examples, the measurement device 100 may not be comprised within a single housing, i.e., some features of the measurement device 100 may not be comprised in the same housing as other features, though the features may still be operably connected with one another. The measurement device 100 includes one or more measurement sensors 101. The measurement sensors 101 are configured to collect measurement data which is indicative of one or more physical dimensions of an area being surveyed by the measurement device 100. The one or more measurement sensors 101 include a Lidar sensor. The Lidar sensor comprises an emitter and a receiver. The emitter is a source of photons. For instance, the emitter may comprise one or more vertical cavity surface emitting laser (VCSEL) cells. The receiver detects photons. For instance, the receiver may comprise one or more single-photon avalanche diode (SPAD) sensors. Other types of emitters and / or receivers may be employed within the Lidar sensor(s). The person skilled in the art may be acquainted with other examples of various types of emitters and / or receivers suitable for use in such a Lidar sensor. The Lidar sensor works by emitting photons, the photons reflecting off a surface in the area and then being detected by the receiver. The time between emission and detection of a photon can be used to determine the distance between the Lidar sensor and the surface off which the photon was reflected. The measurement data may be indicative of the relevant displacements of a plurality of points on the surfaces of solid objects in the area being surveyed. The measurement data may be indicative of the relative positions of at least two surfaces in the area. The measurement data may be collected in the form of a point cloud. The measurement sensors 101 may further include an infrared sensor and / or an image sensor. A mixture of different types of sensors may permit the collection of more accurate and detailed measurement data than a single type of sensor. Data collected by the image sensor and / or the infrared sensor may be combined with data collected by the Lidar sensor to obtain more accurate and detailed measurement data than using the Lidar sensor alone. The measurement device 100 may comprise a camera. The camera may be configured to take one or more pictures of the area before, during, and / or after the measurement sensors 101 collects the measurement data indicative of one or more physical dimensions of the area being surveyed. The picture(s) may be used to provide texture to any models that are subsequently created based on the collected measurement data. The picture(s) may be used to check the veracity of the measurement data collected by the measurement device 100. The picture(s) may be compared to any model representations created based on the collected measurement data to check the veracity of said model representations. The picture(s) may be used to assist in the creation of an accurate model representation of the area. The measurement device 100 includes one or more usage sensors 103. The usage sensor(s) 103 is / are configured to collect usage data that is indicative of how the measurement device 100 is being used while it is collecting measurement data. The usage data may be indicative of a position and / or an orientation and / or a movement of the measurement device 100 while it is being used to obtain the measurement data. When the measurement device 100 is comprised within a single housing, the usage data may pertain to the measurement device 100 as a whole by virtue of the measurement device 100 being within the single housing. When the measurement device 100 is not comprised within a single housing, the usage data may pertain to one or more of the measurement sensors 101. In the present example, the measurement device 100 is comprised within a single housing. The one or more usage sensors 103 may include an accelerometer and / or an inclinometer and / or a gyroscope and / or one or more other sensors suitable for measuring or determining a position and / or an orientation and / or a movement of the measurement device 100. The usage data obtained may be indicative of an instantaneous position of the measurement device 100 relative to a fixed spatial point. The fixed spatial point may be the spatial point at which the measurement device 100 was when the measurement device 100 began to collect measurement data. The usage data obtained may be indicative of the instantaneous orientation of the measurement device 100. The usage data obtained may be indicative of the instantaneous position of the measurement device 100. The usage data obtained may be indicative of the instantaneous velocity of the measurement device 100. The usage data obtained may be indicative of the instantaneous acceleration of the measurement device 100. The usage data may be indicative of a closest and / or a furthest distance between the measurement device 100 and a surface of the area being surveyed. The usage data obtained may be indicative of a rate of change of the orientation of the measurement device 100. The usage data, in particular the position and orientation of the measurement device 100 when the measurement device 100 is comprised in a single housing, or the Lidar sensor when the measurement device 100 is not comprised in a single housing, may be combined with the measurement data collected by the Lidar sensor. Knowing the orientation of the measurement device 100 or Lidar sensor may allow the direction in which the Lidar sensor emits photons to be determined. Knowing the position of the measurement device 100 relative to a fixed point may allow a relative position of the Lidar sensor to be known. Knowing the position and orientation of the Lidar sensor relative to its starting point when measurement began while using the Lidar sensor may allow a 3D map of surfaces in the area to be determined. Another effect of the usage sensor(s)’ 103 collection of usage data is that such usage data may be used to determine if the measurement device 100 is being used in a manner that allows the collection of valid measurement data, i.e. measurement data that is congruent with the actual physical dimensions of the area being surveyed. The usage data may be used to determine if and which parts of the measurement data may not be valid. The usage data may be used to give feedback to a user of the measurement device 100 in order to assist them in using the measurement device 100 in a manner that allows the collection of valid measurement data. Using the measurement device 100 without orienting it correctly or by using it with erratic movements may not allow valid measurement data to be collected. In some examples, the measurement device 100 may not comprise any usage sensors 103. The measurement device 100 comprises a communication interface 104. The communication interface 104 may enable the measurement device 100 to communicate with a server and / or a device remote from the measurement device 100. The communication interface 104 may enable the measurement device 100 to communicate, for example, via a mobile network, Bluetooth® and / or Wi-Fi. An effect of having a communication interface 104 is that it may permit remote connectivity between the measurement device 100 and a server and / or a device remote from the measurement device 100. In some examples, the measurement device 100 may not comprise a communication interface 104. The measurement device 100 comprises one or more indicating devices 105. The indicating devices 105 may comprise a visual and / or an aural and / or a haptic indication device. The indicating devices 105 may comprise a screen and / or a speaker and / or a vibratory device. The indicating devices 105 are configured to allow the measurement device 100 to communicate with a user, e.g. to provide feedback to the user. An effect of the indicating devices 105 is that they enable the measurement device 100 to communicate with a user, e.g. to provide feedback to the user. In some examples, the measurement device 100 may not comprise any indicating devices 105. The measurement device 100 comprises one or more input devices 106. The input devices 106 may comprise one or more buttons and / or one or more touchscreens and / or one or more microphones. The input devices 106 are configured to allow a user to communicate with the measurement device 100. In some examples, the measurement device does not comprise any input devices 106. The measurement device 100 may comprise a processor 102. The processor 102 is configured to execute instructions. The processor 102 may include one or more processing units for executing instructions. The processor 102 is operatively coupled to the measurement sensor(s) 101, the usage sensor(s) 103, the communication interface 104, the indicating device(s) 105, and the input device(s) 106. The processor 102 is configured to interpret user inputs received via the input device(s) 106 and to initiate the collection of measurement data. The processor 102, in some examples, may be configured to convert the measurement data into a mesh. The processor 102, in some examples, may be configured to analyse the usage data collected by the usage sensor(s) 103. The processor 102 may be configured to control what is displayed / indicated by the indicating device(s) 105. The processor 102 may be configured to interpret data from the Lidar sensor(s) and create a 3D point cloud. The processor 102 may be configured to combine data from the Lidar sensor(s) and the usage sensor(s) and, optionally, the image sensor (if present) and / or any other measurement sensors 101 (if present), to create a 3D point cloud. The features of the measurement device 100 in Figure 1 are shown to be comprised within a single housing schematically. However, in other examples, the measurement device 100 may not be comprised within a single housing. For example, the indicating device(s) 105 and / or the input device(s) 106 may be comprised separately from the remaining features of the measurement device 100. The measurement device 100 may also comprise a memory (not shown in Figure 1). The memory may be a non-transitory medium. The memory may store any measurement data collected by the measurement device. The memory may store instructions that may be used by the processor 102. Figure 2 shows a flow diagram 200 for a method of collecting measurement data indicative of one or more physical dimensions of an area being surveyed for a stairlift. At step 201, measurement data is collected using a measurement device, e.g. a measurement device according to the present disclosure. For example, the measurement device may be the measurement device 100 described in relation to Figure 1, the measurement device 500 described in relation to Figure 5a and Figure 5b or the measurement device 601 described in relation to Figure 6a and Figure 6b. The measurement device may comprise more or fewer features than the measurement device 100 described in relation to Figure 1. In implementations, the measurement device may comprise any combination of the features described in relation to Figure 1. The measurement data is obtained by a Lidar sensor comprised in the measurement device. The measurement data is indicative of one or more physical dimensions of the area being surveyed. The measurement data may be indicative of the relevant displacements of a plurality of points on the surfaces of solid objects in the area. At step 201, the measurement device may also collect usage data while it is being used to obtain measurement data. The usage data may be indicative of how the measurement device is being used while it is obtaining measurement data. The usage data is obtained using one or more usage sensors comprised in the measurement device. A first loop 210 proceeds from step 201 to step 202 to step 206 and then back to step 201 while the measurement device is being used to collect measurement data. At step 202, the measurement device analyses the usage data. At step 206, the measurement device gives feedback to the user based on the analysis of the usage data performed at step 202. The analysis and collection of usage data may occur simultaneously. The feedback given in step 206 may be given in real-time to the user based on real-time analysis of the usage data. At step 202, the measurement device analyses the usage data. In this example, the usage data is analysed by comparing it to threshold values. The values may be single values or ranges of values. In implementations, the threshold values may include any one or more of a minimum and / or a maximum orientation of the measurement device, boundaries for the position of the measurement device, a minimum and / or a maximum velocity of the measurement device, a minimum and / or a maximum acceleration of the measurement device, a minimum distance between the measurement device and the boundary of the area being measured, and / or a maximum distance between the measurement device and the boundary of the area being measured. Generally, the threshold values may be threshold values for anything measured as usage data by the usage sensor(s). For instance, the comparison between the usage data and the threshold values may return a single or multiple Boolean values. The comparison may return a value from a range of values, e.g. between 0 and 1, said value being indicative of the result of the comparison. The value returned from a range of values may be indicative of how far from the centre of the range of threshold values the compared usage data parameter is. The analysis of the usage data may allow the measurement device to determine if it is being used in the correct manner to obtain valid measurement data. The measurement device may determine that it is being used in the correct manner if the results of the comparisons performed between the usage data and the threshold values confirms that the usage data is within the threshold values. This analysis may be performed by a processor comprised in the measurement device. The processor is operably connected to the usage sensors. The measurement device may comprise a non-transitory storage wherein instructions are stored. The threshold values and / or the instructions for comparisons may be stored in the non-transitory storage. In some examples, the non-transitory storage need not be part of the measurement device and the threshold values and instructions for comparisons may be stored in the cloud and the measurement device may be connected to the cloud through a wired or wireless network connection. At step 202, usage data may be combined with measurement data collected by the Lidar sensor in order to create a 3D map of surfaces in the area. Measurement data collected by one or more other measurement sensors comprised in the measurement device, such as an image sensor, may be combined with measurement data collected by the Lidar sensor in order to create a 3D map of surfaces in the area. This combination of data may be performed by the processor mentioned above. Knowing the orientation of the Lidar sensor may allow one to know which direction photons are emitted in. The distance that is determined using the time-of-flight method thus becomes a distance from the Lidar sensor in the known direction to a surface. Knowing the position of the Lidar sensor relative to a fixed point, for example the starting point at which the Lidar sensor was at when it began to be used to collect measurement data, may allow the relative positions of different surfaces determined to exist in the area by the Lidar sensor to be known. Combining this knowledge of the orientation and position of the Lidar sensor may allow a 3D map of surfaces in the area to be created. The position and orientation of the Lidar sensor may be measured each time a pulse of photons is emitted and / or received by the Lidar sensor. The processor may convert the time measurement into a distance measurement using the time-of-flight formula: distance = ½ x (speed of light x time of flight). After step 202, the method proceeds to step 206. At step 206, the user is given positive or negative feedback depending upon whether the analysis performed in step 202 determined that the measurement device is not being used in the correct manner. If the measurement device is being used in the correct manner, positive feedback is given to the user at step 206. If the measurement device is being used in an incorrect manner, negative feedback is given to the user at step 206. The measurement device may be configured to display a negative feedback indication and / or may be configured to give an aural negative feedback indication and / or may be configured to give a haptic negative feedback indication. The user may also be given an indication as to how they are using the measurement device incorrectly and, optionally, how to correct their usage of it. In implementations, the user may be given positive feedback depending upon whether the analysis performed in step 202 determined that the measurement device is being used in the correct manner. Examples of how feedback may be given to the user will be described below with reference to Figures 3a-3c. A second loop 211 proceeds from step 201 to step 203 to step 204 to step 205 and then back to step 201 while the measurement device is being used to collect measurement data. At step 203, the measurement device identifies horizontal surfaces that may be implied by the measurement data. These horizontal surfaces may correspond to the horizontal surfaces of steps in the area being surveyed. These horizontal surfaces may correspond to the ground before the start of a staircase in the area. These horizontal surfaces may correspond to any landings that are associated with or comprised in a staircase in the area. The measurement device may infer the presence of these horizontal surfaces by checking for co-planar points in the measurement data. The measurement device may infer a horizontal surface if a number of points that are co-planar to one another exceeds a threshold number. The measurement device may infer that the horizontal surface corresponds to the extent of these co-planar points. The measurement device in this example may comprise a camera. The camera may be used to produce an augmented reality (AR) live feed on a display of the measurement device. The measurement device may be configured to overlay inferred horizontal surfaces on the live feed from the camera. The user may then select an inferred horizontal surface to focus measurement data collection on that surface. The user may select inferred horizontal surfaces that corresponds to steps and / or landings of, or associated with, a staircase in the area being surveyed. The method then proceeds to step 204. At step 204, the user focuses the measurement device on the collection of measurement data on the inferred horizontal surface for a period of time. This may be done by the user pointing the measurement device at the horizontal surface they have selected. The measurement device may provide the user with a countdown of, for example, 5 seconds, for which they are to focus on the inferred horizontal surface before proceeding with the collection of measurement data from the rest of the area being surveyed. At step 205, the measurement device, or the user of the measurement device, determines whether the data collection is complete. The measurement device may determine this based at least in part on a total time elapsed since the measurement device began recording measurement data. The measurement device may determine whether the data collection is complete based at least in part on a computed coverage of the area by the Lidar measurement. The measurement device may determine whether the data collection is completed based at least in part on the density of the point cloud it has gathered. In general, the measurement device may have a threshold value to which it compares a variable corresponding to the amount and / or quality of measurement data obtained to determine whether the data collection is complete or not. The user may determine that the data collection is complete once all stairs and landings in the area have been scanned individually according to steps 203 and 204. If, at step 205, the data collection is complete, the method proceeds to step 402 which will be described later in the flow diagram 400 of Figure 4. If, at step 205, the data collection is not yet complete, the method returns to step 201. Figures 3a-3c show an example of how a measurement device may give feedback to a user while it is being used to collect measurement data. Referring generally to Figures 3a-3c, a measurement device is being used to collect measurement data as in step 201 as described above in reference to Figure 2. The measurement device being used comprises an indicating device, and a usage sensor. The indicating device is a display screen that a user can view. The usage sensor is configured to determine the orientation of the measurement device. The usage sensor is an inclinometer. Figure 3a shows a screenshot 300a of the display screen of the measurement device while it is being used to collect measurement data. The usage sensor measures an orientation of the measurement device with respect to the horizontal, hereafter referred to as the pitch of the measurement device, while the measurement device is being used to collect measurement data. The pitch of the measurement device may be considered to be usage data as described earlier. The pitch of the measurement device can be important in obtaining valid measurement data when collecting measurement data about an area which is being surveyed for a stair-lift. Such areas typically, but not always, comprise one or more staircases. Staircases typically comprise a plurality of surfaces that are horizontal or at least substantially horizontal and a plurality of surfaces that are vertical or at least substantially vertical. A Lidar sensor that is oriented such that it is parallel or substantially parallel to the horizontal may be unable to obtain valid measurement data about any vertical surfaces in the area being surveyed for a stairlift. A Lidar sensor that is oriented such that it is parallel or substantially parallel to the vertical may be unable to obtain valid measurement data about any horizontal surfaces in the area being surveyed for a stairlift. The optimal pitch for obtaining measurement data using a Lidar sensor in such a setting has been found empirically to be equal to the angle of the incline of the staircase with respect to the vertical. Acceptable pitches may be within a range either side of the optimal pitch. For example, acceptable pitches may be within a range of ±40°, ±30°, ±20°, ±10° or ±5°of the optimal pitch. In screenshot 300a, outline 303 shows a horizontal surface that has been identified by the measurement device in the area. This horizontal surface corresponds to the third step from the bottom of the area. The measurement device also comprises a processor. The processor is configured to analyse the pitch of the measurement device and determine whether it is within a first threshold range of values and whether it is within a second threshold range of values wherein the two threshold ranges of values are such that: • the first threshold range of values = [a, b] • the second threshold range of values = [c, d] wherein c is less than a, and b is less than d. The measurement device is configured to give feedback to the user based on its analysis of its pitch. In the example shown in Figure 3a, the analysis of the pitch of the measurement device is fed back to the user using a threshold box 301 and a pitch indicator 302a. The threshold box 301 and the pitch indicator 302a appear in the bottom left corner of the screen as translucent, rectangular overlays. The pitch indicator 302a has a smaller area than the threshold box 301. The position of the pitch indicator 302a relative to the threshold box 301 serves as the means of feedback to the user. In Figure 3a, the analysis of the pitch of the measurement device is such that the pitch is determined to sit within the first threshold range of values, i.e., the pitch of the device is determined to be such that a <pitch <b. In Figure 3a, the pitch indicator 302a is disposed such that it is completely within the threshold box 301, i.e., no part of the pitch indicator 302a extends beyond the edges of the threshold box 301. The user is thus provided with feedback that they are using the measurement device correctly in regard to orienting it with the correct pitch. In some examples, when the pitch of the measurement device is within the first threshold range of values, i.e. a <pitch <b, it may also have a green colour - thereby acting as a clearer feedback indicator for a user. Figure 3b shows another screenshot 300b of the same measurement device being used to collect measurement data. In Figure 3b, the analysis of the pitch of the measurement device is such that the pitch is determined to exceed the lower range of the first threshold range of values but to be within the second threshold range of values, i.e., the pitch is determined to be such that c <pitch <a. In Figure 3b, the pitch indicator 302b is disposed such that a portion of the pitch indicator 302b is within the threshold box 301, and a portion of the pitch indicator 302b extends beyond the threshold box 301. The user is thus provided with feedback that they are not using the measurement device optimally in regard to orienting it with the correct pitch. The portion of the pitch indicator 302b that extends beyond the threshold box 301 extends beyond a lower edge of the threshold box 301. The user is thus informed that they have oriented the measurement device at too shallow a pitch to be optimal, i.e., the angle between the Lidar sensor of the measurement device and the horizontal is too small to be optimal. In some examples, when the pitch of the measurement device is such that pitch of the measurement device exceed the lower range of the first threshold range of values but is within the second threshold range of values, i.e., the pitch is determined to be such that c <pitch <a, it may also have an amber colour - thereby acting as a clearer feedback indicator for the user. Figure 3c shows another screenshot 300c of the same measurement device being used to collect measurement data. In Figure 3c, the analysis of the pitch of the measurement device is such that the pitch is determined to exceed the lower range of the second threshold range of values, i.e., the pitch is determined to be such that pitch <c. In Figure 3c, the pitch indicator 302c is disposed such that it is entirely outside the threshold box 301. The user is thus provided with feedback that the measurement device is oriented with a pitch that is not suitable for the collection of valid measurement data. The pitch indicator 302c is disposed entirely below a lower edge of the threshold box. The user is thus informed that they have oriented the measurement device at too shallow a pitch to obtain valid measurement data, i.e., the angle between the Lidar sensor of the measurement device and the horizontal is too small for the collection of valid measurement data. Valid measurement data is measurement data that is indicative of the physical dimensions of the area being measured. In some examples, when the pitch of the measurement device is such that it exceeds the lower range of the second threshold of values, i.e., the pitch is determined to be such that pitch <c, it may also have a red colour - thereby acting as a clearer feedback indicator for the user. The same method may be used to give feedback to the user when the pitch is determined to be too steep, i.e., the angle between Lidar sensor and the vertical is too large. In this case, the pitch indicator would be partially disposed within the threshold box and partially outside the threshold box such that the pitch indicator extends beyond an upper edge of the threshold box when the pitch is determined to exceed the lower range of the first threshold range of values, i.e. the pitch is determined to be such that b <pitch <d. The pitch indicator would be disposed completely outside the threshold box such that the pitch indicator is disposed beyond the upper edge of the threshold box when the pitch is determined to exceed the upper range of the second threshold range of values, i.e., the pitch is determined to be such d <pitch. The movement of the pitch indicator relative to the threshold box may be continuous and correspond to the instantaneous pitch. The colour of the pitch indicator may vary from green to amber to red as the pitch changes. The colour of the pitch indicator may vary continuously. Figure 4 shows a flow diagram 400 for an example of a method of surveying, designing, and installing a stairlift in an area. At step 401 a user initiates a survey of an area for a stairlift and uses a measurement device to collect measurement data. At step 402 a model representation of the area is created based on the measurement data that is suitable for use in designing a stairlift. At step 403 a stairlift is designed using the model representation created at step 402. At step 404, stairlift components are delivered and installed at the site of the survey according to the designed stairlift. The measurement device in this example may be any measurement device according to the present disclosure, e.g. the measurement device 100 described above in relation to Figure 1. The measurement device may be operated by the user by holding it in their hands or it may be mounted to a device configured to stabilise the measurement device in use, such as a tripod or a gimbal. The measurement device may stay in one position while it is being used to collect measurement data or the measurement device may be moved while it is being used to collect measurement data. Use of the measurement device to collect measurement data may comprise a combination of periods wherein the measurement device is maintained in a constant position and wherein the measurement device is moved. In some examples, the user may be a sales representative. In other examples the user may be an owner, or someone acting on behalf of the owner of the site that is being surveyed for a stairlift. The measurement device comprises one or more measurement sensors. The one or more measurement sensors include a Lidar sensor. At step 401, the Lidar sensor is used to collect the measurement data. The Lidar sensor may allow the collection of more accurate measurement data than manual measurements carried out with, for example, a tape measure, or than photogrammetry methods. The Lidar sensor may allow the collection of measurement data more quickly than manual or photogrammetry methods. The Lidar sensor may reduce the user skill level necessary to obtain valid measurement data. Manual measurements and photogrammetry both require a greater deal of user skill in order to obtain valid measurement data than the Lidar sensor used in the present example does. The measurement data is indicative of one or more physical dimensions of the area being surveyed. The measurement data may be indicative of the relevant displacements of a plurality of points on the surfaces of solid objects in the area. The measurement data may be indicative of the relative positions of at least two surfaces in the area. The measurement data may be obtained in the form of a point cloud. Further details on how the measurement device is used to collect measurement data have been explained earlier with reference to Figure 2. Once the measurement device has completed obtaining measurement data of the area, the measurement device may create a mesh based on the measurement data. In some examples, a mesh may be continuously created and updated based on the measurement data collected while the measurement data is collected. When the measurement device comprises a processor, the processor may be configured to create the mesh based on the measurement data. When the measurement device comprises at least one indicating device, such as a display screen, the measurement device may display a representation of the created mesh using the indicating device to a user. When the measurement device comprises input devices, they may allow the user to communicate their rejection or acceptance of the mesh. Rejecting the mesh may return the method to step 401, allowing the user to restart the collection of measurement data. Accepting the mesh may continue the method to step 403. When a mesh is created by the measurement device, accepting the mesh may cause the measurement data to be uploaded to a server. In some examples, the mesh created by the measurement device may be uploaded to the server instead of or in addition to the measurement data. In this example, the server automatically imports and processes the measurement data into one or more computer aided design (CAD) parts. A CAD part may be a portion of the area represented as a 3D solid or surface that can be used for CAD purposes, In some examples, wherein the mesh is uploaded to the server instead of, or in addition to, the measurement data, the server may be configured to automatically import and process the mesh (and measurement data if relevant) into one or more CAD parts. In some examples, the measurement device is configured to process the measurement data and / or the mesh into one or more CAD parts, and then to upload the CAD part(s) to a server. In some examples, the measurement device may not create the mesh based on the measurement data. In these examples, the measurement device may, upon completion of collecting the measurement data, transmit the measurement data to a remote server. The remote server may generate a mesh based on the measurement data. The remote server may then transmit the mesh to the measurement device whereupon the measurement device visually displays a representation of the mesh to the user. The user may then reject or accept the mesh. Rejecting the mesh may return the method to step 401, allowing the user to restart the collection of measurement data. Accepting the mesh may continue the method to step 403. In the examples where the server creates the mesh, the server may automatically import and process the measurement data into the mesh. The server may be configured to automatically process the measurement data it receives into one or more CAD parts if the mesh is accepted by the user. The server may be configured to automatically process the mesh it has created into one or more CAD parts if the mesh is accepted by the user. At step 402, a model representation of the area is created based on the measurement data. In some examples, an operative remote from the area being surveyed creates a model representation of the area using the CAD part(s) created at step 401. The operative may receive the CAD part(s) from the server. The operative may receive the CAD part(s) from the measurement device. In some examples, the model representation may be created automatically by the server by processing the CAD part(s). In these examples, an operative is not needed to create the initial model representation. An operative may still be involved in checking the suitability of the model representation created by the server. In some examples, the model representation may be created automatically by the measurement device by processing the CAD part(s). In these examples, an operative is not needed to create the initial model representation. An operative may still be involved in checking the suitability of the model representation created by the measurement device. At step 403, a stairlift is designed using the model representation created in step 402. In some examples, an operative uses the model representation created in step 402 and designs a stairlift. In other examples, the server is configured to automatically design a stairlift using the model representation created in step 402. In these examples, an operative is not needed to design the stairlift for the area but may still check the suitability of the stairlift designed by the server and / or edit the design until it is deemed suitable. Designing of the stairlift, whether by an operative or by the server, may be done using a CAD program on a computing device. Designing of the stairlift, whether by an operative or by the server, may include cost constraints that need to be satisfied such that the cost of installing the designed stairlift falls at or below a cost threshold. The cost threshold may be determined by a budget decided upon by an owner, or someone acting on behalf of the owner, of the area in which a stairlift is to be installed. Designing of the stairlift may include producing an estimate of the cost of installing such a stairlift. In some examples, once a stairlift has been designed for the area, a final product model representation may be created that shows a model of how the installed stairlift will appear in the area. This final product model may be communicated to the measuring device and displayed to an owner, or someone acting on behalf of the owner, of the area being surveyed in order to allow them to approve or disapprove the design. The final product model may be displayed by any suitable means to the owner or occupier, or someone acting on behalf of the owner or occupier, of the area being surveyed. Once the stairlift design has been finalised, the method continues to step 404. At step 404, the parts necessary to build and install the stairlift according to the stairlift designed in step 403 are delivered to the area that was surveyed and installed. Before the parts are delivered and installed, one or more of the parts may be manufactured. Figure 5a shows an example of a measurement device 500. The measurement device 500 is shown such that a front surface 501a of the measurement device 500 is visible. The measurement device 500 is comprised within a single housing and is substantially cuboidal. The front surface 501a of the measurement device 500 comprises a display 502a. Figure 5b shows the same example of the measurement device 500 of figure 5a. In Figure 5b, the measurement device 500 is shown such that a rear surface 501b of the measurement device 500 is visible. The rear surface 501b of the measurement device is opposite the front surface 501a of the measurement device. The rear surface 501b of the measurement device 500 comprises a Lidar sensor 502a. The Lidar sensor 502a is arranged such that it is oriented parallel to the rear surface 501b of the measurement device 500. The receiver and transmitter of the Lidar sensor 502a face away from the rear surface 501b. Figure 6a schematically shows a measurement device 601 being used to survey an area 600. The area 600 contains a staircase 602. The staircase 602 has an incline angle 603 relative to the horizontal. Typically, this angle may be from 30 to 50 degrees. The measurement device 601 is the same as the measurement device 500 depicted in Figures 5a and 5b. The measurement device 601 has a pitch angle 604. The pitch angle 604 is defined as the angle between the measurement device 601 and the horizontal. The pitch angle 604 in this example is equal to the incline angle 603 of the staircase 602. Empirically, it has been found by the applicant that the optimal pitch angle for collecting valid measurement data when surveying an area comprising an incline is one that is equal to the incline angle of the incline. The measurement device 601 is oriented such that its rear surface is parallel to the incline of the staircase. The rear surface of the measurement device 601 also faces towards the staircase 602. The Lidar sensor is arranged on the rear surface of the measurement device 601 and therefore is also parallel to the incline of the staircase and faces towards the staircase. The measurement device 601 collects measurement data using the Lidar sensor. Laser light is emitted by the Lidar sensor and reflects off solid surfaces in the area 600. The reflected laser light is then received by the Lidar sensor. The time between emission and reception of laser light by the Lidar sensor is the data that is collected using the Lidar sensor - this is known as time-of-flight data. In this example, the laser light emitted by the Lidar sensor reflects off the staircase 602 and is detected by the Lidar sensor. Three laser light pulse paths are shown in Figure 6a. A first laser light pulse path 605 is shown in Figure 6a. The time of flight of the first laser light pulse path 605 is used to determine a distance between the measurement device 601 and a first point on a surface of the staircase 602. A second laser light pulse path 606 is shown in Figure 6a. The time of flight of the second laser light pulse path 606 is used to determine a distance between the measurement device 601 and a second point on the surface of the staircase 602. A third laser light pulse path 607 is shown in Figure 6a. The time of flight of the third laser light pulse path 607 is used to determine a distance between the measurement device 601 and a third point on the surface of the staircase 602. The Lidar sensor is configured to measure the angle of incidence of the incoming laser light pulses. The person skilled in the art is acquainted with how this is done. The measurement device 601 also comprises one or more usage sensors. The usage sensors are configured to measure an orientation and a position of the measurement device 601. The position of the measurement device 601 is measured relative to a fixed point, in particular to the point at which the measurement device 601 was at when it began to be used to collect measurement data. The orientation of the measurement device comprises the pitch angle 604. Combining the information about the orientation and position of the measurement device allows a 3D map of surfaces in the area 600 to be created. Figure 6b shows the same set up as Figure 6a but the measurement device 601 has now been moved from the position it was at in Figure 6a. The position of the measurement device 601 in Figure 6a is shown in Figure 6b as a dashed outline 602b. The measurement device 601 is again collecting measurement data using the Lidar sensor. Laser light is emitted by the Lidar sensor and reflects off the staircase 602. Three laser light pulses are shown in Figure 6b. A fourth laser light pulse path 603b is shown in Figure 6b. The time of flight of the fourth laser light pulse path 603b is used to determine a distance between the measurement device 601 and a fourth point on a surface of the staircase 602. A fifth laser light pulse path 604b is shown in Figure 6b. The time of flight of the fifth laser light pulse path 604b is used to determine a distance between the measurement device 601 and a fifth point on the surface of the staircase 602. A sixth laser light pulse path 605b is shown in Figure 6b. The time of flight of the sixth laser light pulse path 605b is used to determine a distance between the measurement device 601 and a sixth point on the surface of the staircase 602. The usage sensors of the measurement device 601 can determine the position of the measurement device 601 relative to its position in Figure 6a. The relative positions of the first, second, and third points on the surface of the staircase 602 and the fourth, fifth, and sixth points on the surface of the staircase 602 can thus be determined. The measurement device 601 can thus be used to determine the relative positions and spatial extents of a plurality of surfaces in the area 600. The illustrations of the examples described herein are intended to provide a general understanding of the structure of the various examples. The illustrations are not intended to serve as a complete description of all the elements and features of apparatus and systems that utilise the structures or methods described herein. Many other examples may be apparent to those of skill in the art upon reviewing the disclosure. Additionally, the illustrations are merely representational and may not be drawn to scale. Certain proportions within the illustrations may be exaggerated, while other proportions may be minimised. Accordingly, the disclosure and figures are to be regarded as illustrative rather than restrictive. While this specification contains many specifics, these should not be construed as limitations on the scope of the invention or of what may be claimed, but rather as a description of features specific to particular implementations. Certain features that are described in this specification in the context of separate examples can also be implemented in combination in a single example. Conversely, various features that are described in the context of a single example can also be implemented in multiple examples separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excides from the combination, and the claimed combination may be directed to a subcombination or variation of a sub-combination. This disclosure is intended to cover any and all subsequent adaptations or variations of various examples. Combinations of the above examples, and other examples not specifically described herein, should be apparent to those of skill in the art upon reviewing the description. It is intended that the foregoing detailed description be regarded as illustrative rather than limiting and it is understood that the following claims including all equivalents are intended to define the scope of the invention. The claims should not be read as limited to the described order or elements unless stated to that effect. Therefore, all examples that come within the scope and spirit of the following claims and equivalents thereto are claimed as the invention. It will be understood that the invention is not limited to the embodiments described above. Various modifications and improvements can be made without departing from the concepts disclosed herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to all combinations and sub-combinations of any one or more features disclosed herein.

Claims

1. A method of surveying an area for a stairlift, the method comprising: using a measurement device comprising one or more measurement sensors to collect measurement data that is indicative of one or more physical dimensions of the area;wherein the one or more measurement sensors include a Lidar sensor.

2. The method according to claim 1, wherein the measurement device comprises one or more usage sensors that are configured to collect usage data that is indicative of how the measurement device is being used while it is collecting measurement data.

3. The method according to claim 2, wherein the measurement device is configured to analyse the usage data to determine if the measurement device is being used in a manner that allows the collection of valid measurement data.

4. The method according to claim 3, wherein the measurement device gives feedback to a user, based on the usage data, on how the measurement device is being used while it is collecting measurement data.

5. The method according to any one of claims 2 to 4, wherein the usage data is indicative of an orientation, a position, a velocity and / or an acceleration of at least a portion of the measurement device.

6. The method according to any one of the preceding claims, wherein the measurement device further comprises one or more indicating devices that are configured to allow the measurement device to communicate with a user.

7. The method according to claim 6, wherein the one or more indicating devices comprises a visual and / or an aural and / or a haptic indicating device.

8. The method according to any one of the preceding claims, wherein the measurement device further comprises one or more input devices that are configured to allow a user to communicate with the measurement device.

9. The method according to claim 8, wherein the one or more input devices includes one or more buttons and / or a touchscreen.

10. The method according to any one of the preceding claims further comprising converting the measurement data into a human-readable format.

11. The method according to claim 10, wherein the measurement device is configured to convert the measurement data into a human-readable format.

12. The method according to claim 10 or claim 11, wherein converting the measurement data into a human-readable format comprises converting the measurement data into a mesh of the area.

13. The method according to claim 12, wherein the measurement device further comprises a camera and, optionally, the measurement device is configured to produce an AR live feed of the area comprised of a video feed from the camera and the mesh of the area.

14. The method according to claim 12 or claim 13 further comprising displaying the mesh to a user and the user accepting or rejecting the collected measurement data based on the mesh displayed to them.

15. The method according to any one of the preceding claims wherein the measurement device is comprised within a single housing.

16. The method according to claim 15, wherein the measurement device is a handheld device.

17. A method of designing a stairlift for an area, the method comprising:surveying an area for a stairlift using the method of any one of the preceding claims;converting the measurement data into a model representation of the area;anddesigning a stairlift for the area using the model representation of the area.

18. The method according to claim 17 when dependent on claim 14 or claim 15 or claim 16 when dependent on claim 14, wherein converting the measurement data into a model representation of the area and designing a stairlift for the area using the model representation of the area only occur if the user accepts the collected measurement data based on the mesh displayed to them.

19. The method according to claim 17 or claim 18, wherein converting the measurement data into a model representation of the area comprises converting the measurement data into one or more CAD parts, and optionally then processing the CAD parts into a model representation of the area.

20. The method according to claim 19 wherein converting the measurement data into a model representation of the area further comprises transmitting the measurement data to a remote server, and optionally the remote server converts the measurement data into one or more CAD parts.

21. The method according to claim 20, wherein converting the measurement data into a model representation of the area using the model representation of the area comprises the remote server transmitting the one or more CAD parts to a remote device or workstation, and the remote device or workstation then processes the CAD parts into a model representation of the area.

22. The method according claim 21, wherein designing a stairlift for the area comprises an operative using the remote device or workstation designing the stairlift for the area.

23. A method of installing a stairlift in an area, the method comprising:designing a stairlift for the area using the method of any one of claims 17 to 22;optionally, manufacturing one or more of the components necessary to instal the designed stairlift; anddelivering and installing the components at the area.

24. A measurement device for surveying an area for a stairlift, the measurement device comprising: one or more measurement sensors, including a Lidar sensor, configured to collect measurement data that is indicative of one or more physical 5 dimensions of the area.

25. A system for surveying an area for a stairlift comprising: the measurement device according to claim 24; and a server remote from the measurement device in communication with the 10 measurement device;wherein the measurement device is configured to transmit measurement data to the server.15

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