A water body remote sensing reflectivity measurement device for unmanned aerial vehicle

Abstract

The present invention provides a water body remote sensing reflectivity measurement device for use onboard an unmanned aerial vehicle, which belongs to the field of water color remote sensing technology and solves the problem of large atmospheric signal interference in the prior art water body spectrum measurement. The device includes a data acquisition module, a main control module and a communication module. The data acquisition module includes a water surface entrance pupil signal measurement spectrometer, a sky light signal measurement spectrometer, and an irradiance signal measurement spectrometer. The main control module is used to receive the signals output by the data acquisition module, input them into the built-in water body remote sensing reflectivity calculation model, obtain the water body remote sensing reflectivity excluding environmental interference, and communicate with the ground control station in real time through the communication module to transmit the water body remote sensing reflectivity. Integrate multiple miniature spectrometers to build a comprehensive measurement system to achieve synchronous acquisition of water body, sky light, and irradiance signals, thereby eliminating environmental interference, realizing quantitative monitoring of effective water body signals, and refined surface array measurement of small watersheds.

Description

Technical Field

[0001] The invention relates to the technical field of water color remote sensing, and in particular to a water body remote sensing reflectivity measuring device used for an unmanned aerial vehicle. Background Art

[0002] At present, there are many rivers and lakes, so it is necessary to monitor the water conditions of rivers and lakes. UAV remote sensing technology has the advantages of flexibility, low cost, simple operation, rapid response and high temporal and spatial resolution. It can operate in complex weather conditions, such as cloudy days, haze weather, etc., and can ignore the influence of atmosphere and clouds at a certain altitude (<1km).

[0003] Most of the existing hyperspectral detection equipment onboard drones are hyperspectral cameras. The spectral resolution of existing hyperspectral cameras is mostly between a few nanometers and tens of nanometers, which is completely insufficient for quantitative monitoring of remote sensing reflectance of water bodies. A hyperspectral camera may focus on spectral measurement in a narrow band range, and cannot perform full-band measurement in a wider spectrum. At the same time, the original spectral signal collected by the existing hyperspectral camera is the brightness of the image pixel, which cannot be directly converted into the remote sensing reflectance of the water body. It can only obtain the relative spectral characteristics of the current environment. The water component accounts for only a small part of the signal, and the atmospheric signal interference is too large. To obtain remote sensing reflectance, it is necessary to eliminate environmental interference and extract only relevant information about the water body.

[0004] In summary, the existing hyperspectral detection equipment onboard drones often has poor effects in the field of quantitative monitoring of water bodies. Summary of the invention

[0005] In view of the above analysis, an embodiment of the present invention aims to provide a water body remote sensing reflectivity measurement device for use on an unmanned aerial vehicle, so as to solve the problem of large atmospheric signal interference in water body spectrum measurement in the prior art.

[0006] The embodiment of the present invention provides a water body remote sensing reflectivity measurement device for use on a drone, including a data acquisition module, a main control module and a communication module; wherein:

[0007] The data acquisition module includes a water surface entrance pupil signal measurement spectrometer, a sky light signal measurement spectrometer, and an irradiance signal measurement spectrometer. The water surface entrance pupil signal measurement spectrometer has a fiber optic probe that is tilted downward at 45° and is used to quantitatively measure the total radiance of the fiber optic probe in the spectrometer as a whole, which is scattered by water and reflected by the water surface. L sw , as the water surface entrance pupil signal; the sky light signal measurement spectrometer, whose fiber optic probe is tilted upward at 45°, is used to quantitatively measure the light signal of the fiber optic probe in the spectrometer after being reflected from the water surface. L sky, as the sky light signal; the irradiance signal measurement spectrometer, whose fiber optic probe is vertically upward, and a cosine corrector is installed on the top of the spectrometer to quantitatively measure the total spectral irradiance signal in the 180° field of view plane vertically upward E d ;

[0008] The main control module is used to receive the signals output by the data acquisition module, input them into the built-in water remote sensing reflectivity calculation model, obtain the water remote sensing reflectivity excluding environmental interference, and communicate with the ground control station in real time through the communication module to transmit the water remote sensing reflectivity.

[0009] The beneficial effects of the above technical solution are as follows: The water body remote sensing reflectance measurement device is designed to solve the problem of large atmospheric signal interference in water body spectral measurement. By collecting irradiance and sky light signals, the water body component signal in the total collected signal is stripped, and the water body remote sensing reflectance is extracted to achieve quantitative and normalized acquisition of water body signals. The use of a spectrometer as an optical signal acquisition source has higher precision and accuracy than an imaging camera, and can be used as a basis for quantitative remote sensing. Integrate multiple miniature spectrometers to build a comprehensive measurement system to achieve synchronous acquisition of water, sky light, and irradiance signals, thereby eliminating environmental interference and achieving quantitative monitoring of effective water body signals. The water body remote sensing reflectance measurement device is integrated into a small UAV platform, abandoning the traditional cumbersome ground manual measurement method, and can achieve refined array measurement of small watersheds.

[0010] Based on the further improvement of the above device, the water body remote sensing reflectivity calculation model includes:

[0011]

[0012]

[0013] In the formula, R rs To eliminate the water body remote sensing reflectivity from environmental interference, E d (0 + ) is the irradiance signal just above the water surface E d , r is the reflectivity of the air-water interface, L w It is the water-leaving radiation rate of the light that enters the water body, is scattered back by the water body, and then enters the optical fiber probe in the spectrometer. L wc It is the information of the white hat on the water. L g It is the random reflection of direct sunlight by waves on the water surface.

[0014] Furthermore, the main control module executes the following procedures to complete the real-time measurement function of water body remote sensing reflectivity:

[0015] S51. Start the measurement at a time when there is no obvious white cap on the water surface and avoid direct sunlight;

[0016] S52. Obtaining data from the water surface entrance pupil signal measurement spectrometer, the sky light signal measurement spectrometer, and the irradiance signal measurement spectrometer, and performing preprocessing;

[0017] S53. Input the pre-processed data of the water surface entrance pupil signal measurement spectrometer, the sky light signal measurement spectrometer, and the irradiance signal measurement spectrometer into the built-in water body remote sensing reflectivity calculation model to obtain the water body remote sensing reflectivity excluding environmental interference. R rs ;

[0018] S54. The water body remote sensing reflectivity excluding environmental interference R rs The system can store data and communicate with the ground control station in real time through the communication module to realize the remote sensing reflectivity of water bodies by the ground control station. R rs Real-time monitoring.

[0019] Furthermore, the water body remote sensing reflectivity measuring device also includes a power supply module; wherein,

[0020] The power module includes a lithium battery pack and communicates with the main control module through a set communication protocol;

[0021] The main control module is also used to monitor the battery power of the power module in real time, and send back an alarm signal to the ground control station when it is identified that the battery power is lower than the alarm value.

[0022] Furthermore, the water surface entrance pupil signal measuring spectrometer, sky light signal measuring spectrometer, and irradiance signal measuring spectrometer are of the same model and have the same weight.

[0023] Furthermore, the main control module adopts the Elsky NUC600-UA motherboard as the central control, has an i7 series CPU, is equipped with standard USB2.0, USB3.0 and HDMI output ports, is equipped with a Win10 system, and is equipped with an SSD hard drive as a data storage device.

[0024] Furthermore, the water body remote sensing reflectivity measuring device also includes a device housing; the main control module, the data acquisition module and the communication module are all arranged inside the device housing; and,

[0025] The water surface entrance pupil signal measurement spectrometer, sky light signal measurement spectrometer, and irradiance signal measurement spectrometer in the data acquisition module all use domestically produced GCS100 micro-spectrometers and are connected to standard SMA interface optical fiber output probes; the water surface entrance pupil signal measurement spectrometer, sky light signal measurement spectrometer, and irradiance signal measurement spectrometer are all fixed to the device casing with screws.

[0026] Furthermore, the communication module includes a 4G LTE communication submodule and a GNSS positioning submodule; wherein,

[0027] The 4G LTE communication submodule includes a Quectel EC800M micro communication board equipped with a 4G sim card;

[0028] The GNSS positioning submodule is fixed on the top of the water body remote sensing reflectivity measuring device, and is used to receive GPS signals and Beidou signals, and after being triggered in real time by the main control module, it continuously records the current precise position information of the water body remote sensing reflectivity measuring device.

[0029] Further, the main control module executes the following procedures:

[0030] S1. Before the UAV executes the flight program, start the system self-check function, including automatically identifying the serial ports of the main control module and the models and equipment numbers of the water surface entrance pupil signal measurement spectrometer, the sky light signal measurement spectrometer, and the irradiance signal measurement spectrometer, and connect the water surface entrance pupil signal measurement spectrometer, the sky light signal measurement spectrometer, and the irradiance signal measurement spectrometer to determine whether each spectrometer is initialized successfully. If so, execute the next step, otherwise, re-execute step S1;

[0031] S2. Cover the optical fiber probes of each spectrometer to collect the background noise optical signal caused by the dark current of each spectrometer under the current covering background;

[0032] S3. Obtain the current ambient light intensity, deduct the base noise light signal caused by the dark current, obtain the actual light intensity, that is, the signal after dark current correction, and then set a unified integration time for the water surface entrance pupil signal measurement spectrometer, the sky light signal measurement spectrometer, and the irradiance signal measurement spectrometer;

[0033] S4. After the UAV executes the flight program, the continuous data recording function of the main control module is started;

[0034] S5. Execute steps S51 to S54, and record the current geographic location through the GNSS module, as well as determine whether at least one signal is too strong or too weak through the signals of the water entrance pupil signal measurement spectrometer, sky light signal measurement spectrometer, and irradiance signal measurement spectrometer that have been synchronously collected and corrected for dark current. If so, automatically adjust the integration time so that the collected signals of each spectrometer fall within a reasonable range, then record the collection results of this time, and start the next cycle until the collection is completed.

[0035] Furthermore, the water body remote sensing reflectivity measuring device is fixedly connected to the external load port of the drone and mounted below the drone.

[0036] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the invention, nor is it intended to limit the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0038] Figure 1 A schematic diagram showing the states of the drone and the water body remote sensing reflectivity measuring device in Example 1 is shown;

[0039] Figure 2 A second schematic diagram of the state of the drone and the water body remote sensing reflectivity measuring device in Example 1 is shown;

[0040] Figure 3 A three-dimensional schematic diagram of a water body remote sensing reflectivity measuring device according to Example 1 is shown;

[0041] Figure 4 A front schematic diagram of a water body remote sensing reflectivity measuring device according to Example 1 is shown;

[0042] Figure 5 A schematic diagram of the back side of the water body remote sensing reflectivity measuring device in Example 1 is shown;

[0043] Figure 6 The internal schematic diagram of the water body remote sensing reflectivity measuring device in Example 1 is shown;

[0044] Figure 7 A schematic diagram showing the composition of a water body remote sensing reflectivity measuring device in Example 1 is shown;

[0045] Figure 8 A schematic diagram showing the basic flow of the water body remote sensing reflectivity measurement device in Example 2 is shown;

[0046] Fig. 9 A schematic diagram of sky light propagation under the influence of water is shown;

[0047] Fig.10 A collection schematic diagram of a water body remote sensing reflectivity measurement device is shown. DETAILED DESCRIPTION

[0048] Embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0049] As used herein, the term "including" and its variations mean open inclusion, i.e., "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "based at least in part on". The terms "an example embodiment" and "an embodiment" mean "at least one example embodiment". The term "another embodiment" means "at least one additional embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0050] In order to solve the problem of airborne acquisition of water body hyperspectral, it is necessary to adopt detection means with higher spectral accuracy and collect ambient light field information to obtain the real water body remote sensing reflectivity. For water bodies, the spatial difference within a small range is not obvious, so airborne equipment can completely reduce the load weight and improve the spectral accuracy by carrying a lightweight spectrometer.

[0051] The following first introduces the key terms and their physical definitions involved in the present invention.

[0052] Ocean Color Remote Sensing: Ocean color remote sensing is a method of obtaining water color information through remote sensing technology, which is used to monitor and study water environment quality, water composition and its changes. Ocean color remote sensing is mainly used to monitor water bodies such as oceans, lakes and rivers. It uses sensors on platforms such as satellites, aircraft or drones to measure the spectral information reflected by water bodies, thereby obtaining information about the physical, chemical and biological properties of water bodies.

[0053] Hyperspectral Remote Sensing: Hyperspectral remote sensing is an advanced remote sensing technology that uses high spectral resolution sensors to capture detailed spectral information of target objects at different wavelengths. Compared with traditional multispectral remote sensing, hyperspectral remote sensing can obtain more band information, thus providing more refined and rich spectral data.

[0054] Remote Sensing Reflectance, ): Remote sensing reflectivity refers to the ratio of the intensity of electromagnetic waves reflected by surface objects to the intensity of electromagnetic waves incident on the object. In remote sensing, reflectivity is a key physical quantity used to quantitatively describe the reflection characteristics of objects to electromagnetic waves of different wavelengths. The measurement and analysis of reflectivity can help users understand the properties and status of surface objects.

[0055] Irradiance: Irradiance refers to the electromagnetic radiation energy received per unit area. It indicates the density of radiation energy distributed on a surface.

[0056] Radiance: Radiance refers to the radiation intensity per unit area and per unit solid angle. It describes the distribution of radiation energy in one direction.

[0057] Spectrometer: A spectrometer is an instrument used to measure the intensity of light at different wavelengths. In remote sensing, a spectrometer can provide information about the composition, state, and changes of surface materials by measuring the spectrum of electromagnetic radiation.

[0058] Integration Time: In spectroscopy, integration time is a key parameter for optical measurement equipment such as spectrometers. It refers to the time period during which the spectrometer collects light signals when performing measurements. The length of this time directly affects the measurement results and performance of the spectrometer, similar to the exposure time in photography. By adjusting the integration time, the total amount of photons received by the sensor can be controlled.

[0059] like Fig. 9 As shown in Figure 1, when light passes from one medium to another, it will be reflected and refracted at the interface. Take sunlight shining on the water surface as an example.

[0060] Reflection: Part of the light is directly reflected back from the water surface. r fixed.

[0061] Refraction: Part of the light passes through the interface and goes underwater. Similarly, when this part of the light encounters an obstacle, it will also be reflected and refracted. Eventually, a small part will return to the water surface, and this small part carries the information of the water body.

[0062] In short, part of the signal goes underwater, and part of the signal is reflected directly back into the air.

[0063] Example 1

[0064] One embodiment of the present invention discloses a water body remote sensing reflectivity measurement device for use on a drone, such as Figure 1-Figure 6 As shown in the figure, the device is mounted under the drone and can solve the problem of small-scale water body signal array extraction and quantification in the field of water color remote sensing in the prior art. Figure 7 As shown, the device includes a data acquisition module, a main control module and a communication module, and has the function of measuring the hyperspectral remote sensing reflectance of water bodies.

[0065] Among them, the data acquisition module includes a water surface entrance pupil signal measurement spectrometer, a sky light signal measurement spectrometer, and an irradiance signal measurement spectrometer.

[0066] The water surface entrance pupil signal measurement spectrometer, whose fiber optic probe is tilted downward at 45°, is used to quantitatively measure the total radiance of the fiber optic probe in the spectrometer as a whole, which is scattered by water and reflected by the water surface. L sw , as the water surface entrance pupil signal.

[0067] The sky light signal measurement spectrometer, whose fiber optic probe is tilted upward at 45°, is used to quantitatively measure the light signal that enters the fiber optic probe in the spectrometer after being reflected on the water surface. L sky , as a sky light signal.

[0068] The irradiance signal measurement spectrometer has a fiber optic probe pointing vertically upward and a cosine corrector installed on the top of the spectrometer to quantitatively measure the total spectral irradiance signal in a 180° vertically upward field of view. E d (The sum of signals within the 180° vertical field of view).

[0069] The main control module is used to receive the signals output by the data acquisition module, input them into the built-in water remote sensing reflectivity calculation model, obtain the water remote sensing reflectivity excluding environmental interference, and communicate with the ground control station in real time through the communication module to transmit the water remote sensing reflectivity.

[0070] Compared with the prior art, the water body remote sensing reflectivity measurement device disclosed in this embodiment is intended to solve the problem of large atmospheric signal interference in water body spectral measurement. By collecting irradiance and sky light signals, the water body component signal in the total collected signal is stripped, and the water body remote sensing reflectivity is extracted to achieve quantitative and normalized collection of water body signals. The use of a spectrometer as an optical signal acquisition source has higher precision and accuracy than an imaging camera, and can be used as a basis for quantitative remote sensing. Integrate multiple miniature spectrometers to build a comprehensive measurement system to achieve synchronous acquisition of water, sky light, and irradiance signals, thereby eliminating environmental interference and achieving quantitative monitoring of effective water body signals. The water body remote sensing reflectivity measurement device is integrated into a small UAV platform, abandoning the traditional cumbersome ground manual measurement method, and can achieve refined array measurement of small watersheds.

[0071] Example 2

[0072] An improvement is made on the basis of Example 1, in which the water body remote sensing reflectivity measuring device is fixedly connected to the external load port of the DJI M350 UAV and mounted under the DJI M350 UAV.

[0073] Preferably, the water body remote sensing reflectivity measuring device includes four major parts: a main control module, a power module, a data acquisition module and a communication module.

[0074] The main control module uses the Elsky NUC600-UA motherboard as the central control, has an i7 series CPU, is equipped with standard USB2.0, USB3.0 and HDMI output ports, is equipped with Win10 system, and is equipped with a 512G SSD hard drive as a data storage device.

[0075] The power module uses a 12V UPS lithium battery pack and is connected to the system to communicate with the main control module through the set IIC communication protocol, so that the main control module can monitor the battery power of the power module in real time, and send an alarm signal back to the ground control station when it is identified that the battery power is lower than the alarm value.

[0076] The data acquisition module consists of three spectrometers of the same model. Each spectrometer uses a domestically produced GCS100 micro-spectrometer, each weighing 400g, and is used to measure the water surface entrance pupil signal, sky light signal, and irradiance signal. Each spectrometer is connected to a standard SMA interface optical fiber output probe. Each spectrometer is fixed to the housing with M3 screws.

[0077] The communication module includes a 4G LTE communication submodule and a GNSS positioning submodule. The 4G LTE communication submodule includes a Quectel EC800M micro communication board equipped with a 4G sim card. The Quectel EC800M micro communication board, connected to the main control module, can realize real-time communication within the scope of the second-class terrestrial water body area, so as to facilitate real-time monitoring by the ground control station. The GNSS positioning submodule is fixed on the top of the water body remote sensing reflectivity measuring device, and is used to receive GPS signals and Beidou signals, and can realize dual-mode signal reception and switching. Moreover, after it is triggered in real time by the main control module, it continuously records the current precise position information of the water body remote sensing reflectivity measuring device.

[0078] Preferably, the main control module executes the following procedures to complete the real-time measurement function of water body remote sensing reflectivity:

[0079] S51. Start the measurement at a time when there is no obvious white cap on the water surface and when it is away from direct sunlight.

[0080] S52. Obtain the data of the water surface entrance pupil signal measurement spectrometer, the sky light signal measurement spectrometer, and the irradiance signal measurement spectrometer, and perform preprocessing.

[0081] S53. Input the pre-processed data of the water surface entrance pupil signal measurement spectrometer, the sky light signal measurement spectrometer, and the irradiance signal measurement spectrometer into the built-in water body remote sensing reflectivity calculation model to obtain the water body remote sensing reflectivity excluding environmental interference. R rs .

[0082] Among them, the water body remote sensing reflectivity calculation model includes:

[0083] (1)

[0084] In the formula, R rs To eliminate environmental interference, remote sensing reflectivity of water bodies; E d (0 + ) is the downward irradiance signal just above the water surface E d For drones, it can be considered that they obtain E d That is E d (0 + ); L w It is the water-leaving radiance of the light that enters the water body, is scattered back by the water body, and then enters the optical fiber probe in the spectrometer.

[0085] In water color remote sensing, the spectral radiance signal above the water surface is composed of:

[0086] (2)

[0087] It can be deduced that:

[0088] (3)

[0089] In the formula, R rs To eliminate environmental interference, remote sensing reflectivity of water bodies; r is the reflectivity of the air-water interface; L wc It is the information of the white cap on the water surface. When there is no white cap on the water surface, its value can be considered as 0. L g It is the random reflection of direct sunlight by waves on the water surface. It does not contain any water body information. For no-wave or micro-wave environments, it can be considered L g is 0; E d (0 + ) is the total spectral irradiance signal in the 180° vertical field of view plane.

[0090] S54. The water body remote sensing reflectivity excluding environmental interference R rs The system can store data and communicate with the ground control station in real time through the communication module to realize the remote sensing reflectivity of water bodies by the ground control station. R rs Real-time monitoring.

[0091] For field measurements, the atmospheric scattering signal can be ignored. Based on this, to obtain the water-leaving radiance, it is necessary to measure the water body entrance pupil signal and the sky light signal, and select the time when there is no obvious white cap on the water surface and avoid direct sunlight. At the same time, in order to ensure the comparability of the measurement results at different times, locations, and atmospheric conditions, normalization is also required. Remote sensing reflectance is usually used for quantitative characterization, see formula (1).

[0092] Therefore, three spectrometers are used to measure the water surface entrance pupil, sky light and irradiance signals respectively. The above calculation can obtain the normalized value that excludes the external environmental change factors, that is, the remote sensing reflectivity of the water body.

[0093] Preferably, the water body remote sensing reflectivity measuring device further comprises a device housing, wherein the main control module, the data acquisition module and the communication module are all arranged inside the device housing.

[0094] Preferably, the main control module executes the following procedures:

[0095] S1. Before the UAV executes the flight program, start the system self-check function, including automatically identifying the serial ports of the main control module and the models and equipment numbers of the water surface entrance pupil signal measurement spectrometer, the sky light signal measurement spectrometer, and the irradiance signal measurement spectrometer, and connect the water surface entrance pupil signal measurement spectrometer, the sky light signal measurement spectrometer, and the irradiance signal measurement spectrometer to determine whether each spectrometer is initialized successfully. If so, execute the next step, otherwise, re-execute step S1;

[0096] S2. Cover the optical fiber probes of each spectrometer to collect the background noise optical signal caused by the dark current of each spectrometer under the current covering background;

[0097] S3. Obtain the current ambient light intensity, deduct the base noise light signal caused by the dark current, obtain the actual light intensity of each spectrometer, that is, the signal corrected by the dark current, and then set a unified integration time for the water surface entrance pupil signal measurement spectrometer, the sky light signal measurement spectrometer, and the irradiance signal measurement spectrometer according to a default value (for example, the default value is selected when a certain relationship or a certain range is satisfied);

[0098] S4. After the UAV executes the flight program, the continuous data recording function of the main control module is started;

[0099] S5. Execute steps S51 to S54, and record the current geographic location through the GNSS module, as well as determine whether at least one signal is too strong or too weak through the signals of the water entrance pupil signal measurement spectrometer, sky light signal measurement spectrometer, and irradiance signal measurement spectrometer that have been synchronously collected and corrected for dark current. If so, automatically adjust the integration time so that the collected signals of each spectrometer fall within a reasonable range, then record the collection results of this time, and start the next cycle until the collection is completed.

[0100] Preferably, the automatic integration time adjustment in step S5, so that the collected signals of each spectrometer fall within a reasonable range, further includes:

[0101] S51. respectively determine the maximum value (maximum light intensity) of the dark current corrected signals of the water surface entrance pupil signal measuring spectrometer, the sky light signal measuring spectrometer, and the irradiance signal measuring spectrometer;

[0102] S52. Automatically set the integration time of the water surface entrance pupil signal measurement spectrometer, the sky light signal measurement spectrometer, and the irradiance signal measurement spectrometer according to the above maximum value;

[0103] S53. respectively obtain the dark current-corrected signals of the water surface entrance pupil signal measuring spectrometer, the sky light signal measuring spectrometer, and the irradiance signal measuring spectrometer after resetting the integration time, and then respectively determine the maximum value (maximum light intensity) of the dark current-corrected signals of the water surface entrance pupil signal measuring spectrometer, the sky light signal measuring spectrometer, and the irradiance signal measuring spectrometer;

[0104] S54. If the maximum value (maximum light intensity) after resetting the integration time exceeds 90% of the corresponding spectrometer range, the integration time of the spectrometer is gradually shortened until the maximum value of the light intensity collected falls within the 10% to 90% light intensity range of the spectrometer;

[0105] S55. If the maximum value (maximum light intensity) after resetting the integration time is identified to be less than 10% of the corresponding spectrometer range, the integration time of the spectrometer is gradually increased until the maximum light intensity value collected falls within the 10% to 90% light intensity range of the spectrometer.

[0106] Steps S51 to S55 automatically set the integration time of each spectrometer according to the maximum value in each spectrometer. When the maximum light intensity exceeds 90% of the spectrometer range, the integration time is gradually shortened. When the maximum light intensity is less than 10% of the spectrometer range, the integration time is gradually increased until the maximum light intensity collected falls within the 10% to 90% light intensity range.

[0107] During implementation, the water body remote sensing reflectivity measurement device is operated in a self-driven power supply mode and is equipped with a control motherboard, which can perform fully autonomous collection. The basic process can be seen Figure 8 . Install the device of the present invention at the load of the drone, turn on the power and start the main control module, and the program will run automatically. The system starts self-checking, automatically identifies the serial port and spectrometer model, equipment number, and connects three spectrometers. When it starts correctly, first measure the dark current of each spectrometer under the current background by covering the optical fiber probe of the spectrometer, and then automatically set a reasonable integration time according to the current ambient light intensity. After the drone executes the flight program, the device starts to record data continuously. The current geographic location is recorded through the GNSS module, and the signals of the three spectrometers are collected synchronously. After the collection, a judgment is made first. When the spectral signal is too strong or too weak, indicating that the integration time exceeds the limit, the integration time is automatically adjusted so that the collected signal falls within a reasonable range. After that, the result is recorded and the next cycle is started until the collection is completed.

[0108] like Fig.10 As shown, the total radiation rate that finally enters the spectrometer on the right is L sw include:

[0109] ① The signal of sunlight passing through the water surface, then reflecting from the bottom of the water or suspended matter in the water, and then passing through the water surface back to the air is called water-leaving radiance (this part passes through the water, so it contains water body information, also known as water-leaving radiance). L w .

[0110] ②Signal from sunlight being directly reflected from the water surface ,in r It is the reflectivity of the air-water interface, a fixed value (it does not pass below the water surface and therefore does not include water information).

[0111] In order to extract the water-off-water radiance that only contains water information (which can be understood as the signal intensity of sunlight returning to the water after passing through the water surface, L w ), to obtain the total radiance from the right spectrometer L sw Subtract the signal reflected from the water surface from the sky light , so two spectrometers, left and right, are needed.

[0112] It can be seen that how much light signal can pass through the water surface and scatter back to the water surface is not only related to the water body conditions, but also to the current intensity of the sunlight itself. The values ​​measured under different conditions cannot be compared, so it is necessary to eliminate the influence of the environment itself (sunlight intensity). This is the value measured by the irradiance signal meter. E d (It can be understood as the current ambient light intensity).

[0113] Compared with Example 1, the water body remote sensing reflectivity measurement device for drone provided in this embodiment has the following beneficial effects:

[0114] 1. Connected to the 4G LTE communication submodule, in addition to full self-driving, it can also be linked to the ground station for monitoring. Specifically, install the device of the present invention at the load of the drone, turn on the power and start the main control module, insert the 4G LTE communication submodule into the sim card and connect it to the main control module to establish a connection with the ground station. After the system self-checks and collects dark current, it will execute the flight mission. After the drone flies to the designated location, the ground end sends a collection command, collects with the specified integration time and average sampling number, and transmits the measurement signal back in real time for the ground end to monitor. At the same time, the power supply surplus is detected in real time, and when the battery power is detected to be too low, an alarm message is sent to the ground so that the ground end can dynamically adjust the flight mission.

[0115] 2. By adjusting the integration time, the total amount of photons received by the spectrometer can be controlled. The acquisition processes of the three spectrometers are independent of each other. At the same time, the integration time can be automatically and synchronously adjusted according to environmental information to meet the requirements of the spectral measurement range and have adjustable control experience.

[0116] Embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terms used herein are selected to best explain the principles of the embodiments, practical applications, or improvements over the prior art, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A water body remote sensing reflectivity measurement device for use on an unmanned aerial vehicle, characterized in that: It includes data acquisition module, main control module and communication module; among which, The data acquisition module includes a water surface entrance pupil signal measurement spectrometer, a sky light signal measurement spectrometer, and an irradiance signal measurement spectrometer. The water surface entrance pupil signal measurement spectrometer has a fiber optic probe that is tilted downward at 45° and is used to quantitatively measure the total radiance L of the fiber optic probe in the spectrometer as a whole, which is scattered by the water body and reflected by the water surface. sw , as the water surface entrance pupil signal; the sky light signal measurement spectrometer, whose fiber optic probe is tilted upward at 45°, is used to quantitatively measure the light signal L that enters the fiber optic probe in the spectrometer after being reflected on the water surface. sky , as the sky light signal; the irradiance signal measurement spectrometer, whose optical fiber probe is vertically upward, and a cosine corrector is installed on the top of the spectrometer to quantitatively measure the total spectral irradiance signal E in the 180° field of view plane vertically upward d ; The main control module is used to receive the signals output by the data acquisition module, input them into the built-in water body remote sensing reflectivity calculation model, obtain the water body remote sensing reflectivity excluding environmental interference, and communicate with the ground control station in real time through the communication module to transmit the water body remote sensing reflectivity; The water body remote sensing reflectivity calculation model includes: L w =L sw -rL sky -L wc -L g In the formula, R rs To eliminate the environmental interference of water remote sensing reflectance, E d (0 + ) is the irradiance signal E just above the water surface d , r is the reflectivity of the air-water interface, L w L is the water-leaving radiation rate of the light that enters the water body and is scattered back by the water body and then enters the optical fiber probe in the spectrometer. wc This is the information of the white hat on the water surface, L g It is the random reflection of direct sunlight by waves on the water surface; The main control module executes the following procedures to complete the real-time measurement function of water body remote sensing reflectivity: S51. Start the measurement at a time when there is no obvious white cap on the water surface and avoid direct sunlight; S52. Obtaining data from the water surface entrance pupil signal measurement spectrometer, the sky light signal measurement spectrometer, and the irradiance signal measurement spectrometer, and performing preprocessing; S53. Input the pre-processed data of the water surface entrance pupil signal measurement spectrometer, the sky light signal measurement spectrometer, and the irradiance signal measurement spectrometer into the built-in water body remote sensing reflectivity calculation model to obtain the water body remote sensing reflectivity R excluding environmental interference. rs ; S54. The water body remote sensing reflectivity R excluding environmental interference rs The module can be used to store and communicate with the ground control station in real time through the communication module, so as to realize the remote sensing reflectivity R of the water body by the ground control station. rs Real-time monitoring; The main control module executes the following procedures: S1. Before the UAV executes the flight program, start the system self-check function, including automatically identifying the serial ports of the main control module and the models and equipment numbers of the water surface entrance pupil signal measurement spectrometer, the sky light signal measurement spectrometer, and the irradiance signal measurement spectrometer, and connect the water surface entrance pupil signal measurement spectrometer, the sky light signal measurement spectrometer, and the irradiance signal measurement spectrometer to determine whether each spectrometer is initialized successfully. If so, execute the next step, otherwise, re-execute step S1; S2. Cover the optical fiber probes of each spectrometer to collect the background noise optical signal caused by the dark current of each spectrometer under the current covering background; S3. Obtain the current ambient light intensity, deduct the base noise light signal caused by the dark current, obtain the actual light intensity, that is, the signal after dark current correction, and then set a unified integration time for the water surface entrance pupil signal measurement spectrometer, the sky light signal measurement spectrometer, and the irradiance signal measurement spectrometer; S4. After the UAV executes the flight program, the continuous data recording function of the main control module is started; S5. Execute steps S51 to S54, and record the current geographic location through the GNSS module, as well as determine whether at least one signal is too strong or too weak through the signals of the water entrance pupil signal measurement spectrometer, sky light signal measurement spectrometer, and irradiance signal measurement spectrometer that have been synchronously collected and corrected for dark current. If so, automatically adjust the integration time so that the collected signals of each spectrometer fall within a reasonable range, then record the collection results of this time, and start the next cycle until the collection is completed.

2. The water body remote sensing reflectivity measuring device for use on a drone according to claim 1, characterized in that: Also includes a power module; wherein, The power module includes a lithium battery pack and communicates with the main control module through a set communication protocol; The main control module is also used to monitor the battery power of the power module in real time, and send back an alarm signal to the ground control station when it is identified that the battery power is lower than the alarm value.

3. The water body remote sensing reflectivity measuring device for use on a drone according to any one of claims 1-2, characterized in that: The water surface entrance pupil signal measuring spectrometer, sky light signal measuring spectrometer and irradiance signal measuring spectrometer are of the same model and have the same weight.

4. The water body remote sensing reflectivity measuring device for use on a drone according to any one of claims 1-2, characterized in that: The main control module uses the Elsky NUC600-UA motherboard as the central control, has an i7 series CPU, is equipped with standard USB2.0, USB3.0 and HDMI output ports, is equipped with a Win10 system, and is equipped with an SSD hard drive as a data storage device.

5. The water body remote sensing reflectivity measuring device for use on a drone according to any one of claims 1-2, characterized in that: It also includes a device housing; the main control module, the data acquisition module and the communication module are all arranged inside the device housing; and, The water surface entrance pupil signal measurement spectrometer, sky light signal measurement spectrometer, and irradiance signal measurement spectrometer in the data acquisition module all use domestically produced GCS100 micro-spectrometers and are connected to standard SMA interface optical fiber output probes; the water surface entrance pupil signal measurement spectrometer, sky light signal measurement spectrometer, and irradiance signal measurement spectrometer are all fixed to the device casing with screws.

6. The water body remote sensing reflectivity measuring device for use on a drone according to any one of claims 1-2, characterized in that: The communication module includes a 4G LTE communication submodule and a GNSS positioning submodule; wherein, The 4G LTE communication submodule includes a Quectel EC800M micro communication board equipped with a 4G sim card; The GNSS positioning submodule is fixed on the top of the water body remote sensing reflectivity measuring device, and is used to receive GPS signals and Beidou signals, and after being triggered in real time by the main control module, it continuously records the current precise position information of the water body remote sensing reflectivity measuring device.

7. The water body remote sensing reflectivity measuring device for use on a drone according to any one of claims 1-2, characterized in that: The water body remote sensing reflectivity measuring device is fixedly connected to the external load port of the UAV and mounted below the UAV.

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