Indoor Positioning via Laser Rangefinder and PDA
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Solution Overview
Problem
Existing positioning systems, such as GPS and RF triangulation, are ineffective within many buildings due to RF opacity and the need for calibrated sensor infrastructure, making it difficult to accurately determine one's location inside a building.
Innovation Solution
A method and apparatus using a laser rangefinder and a handheld computer to translate distance measurements into local and global positions by selecting and digitizing walls in a building's map, allowing for ad-hoc positioning without fixed infrastructure and RF signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GPS or RF triangulation methods are used for positioning, then positioning can be achieved in open spaces, but these methods fail to work effectively within buildings due to RF opacity
Solution Approach 1:
The patent replaces RF electromagnetic field-based positioning with a laser-based optical measurement system. The laser rangefinder uses time-of-flight measurement of laser pulses to determine distances to physical walls, and the PDA uses these measurements combined with a digital map to calculate position. This substitution of optical/mechanical measurement for RF triangulation enables reliable indoor positioning where RF signals are blocked.
2Measurement precision
If fixed sensor infrastructure is deployed for triangulation positioning, then positioning accuracy can be maintained, but the system requires calibrated fixed sensors and uniform signal penetration which are not available in ad-hoc scenarios
Solution Approach 1:
The system uses the building's existing physical structure (walls, floors, ceilings) as the reference framework for positioning. Instead of deploying fixed sensors throughout the building, the portable laser rangefinder and PDA use the building's own geometry—selected via digital map and physically targeted—as the measurement baseline. This self-service approach eliminates the need for external calibrated infrastructure while maintaining positioning accuracy.
Solution Approach 2:
Rather than having fixed sensors emit signals and measure reflections from moving objects, the system inverts the approach: a portable device actively measures distances to fixed architectural features (walls, floors). The reference frame is the building structure itself, and the portable device moves relative to it, collecting range data to compute position through trilateration algorithms.
3Measurement precision
If current laser rangefinders are used, then distance measurement is provided, but there is no provision for translating these distance measurements to local x,y positions and then to global x,y positions
Solution Approach 1:
The patent merges the laser rangefinder with a PDA running specialized positioning software and a digital map of the building. The PDA receives raw distance measurements from the laser rangefinder, combines them with directional information from an electronic compass, and uses the digital map to identify which walls and features are being measured. The system then automatically performs the coordinate transformation from raw distances to local and global position coordinates, eliminating the need for manual calculation.
Solution Approach 2:
The PDA and its software act as an intermediary between the laser rangefinder and the user. The rangefinder provides raw distance data, the PDA processes this data through algorithms that use the digital map to identify target walls, calculate local coordinates relative to those walls, and transform to global building coordinates. This intermediary layer handles the complex coordinate mathematics and presents simplified position information to the user.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Accurately determines position within a building with a mean error of approximately 0.1 meters or better, improving upon existing systems by providing positional information without reliance on RF signals and with reduced user input through the integration of an electronic compass.
Implementation Method 1
pointing and firing a laser rangefinder at corresponding physical walls
Implementation Method 2
Current laser rangefinders simply report the distance from the laser instrument to an object the laser is pointed at
Data Source
AI summary
An apparatus, computer software, and a method of determining position inside a building comprising selecting on a PDA at least two walls of a room in a digitized map of a building or a portion of a building, pointing and firing a laser rangefinder at corresponding physical walls, transmitting collected range information to the PDA, and computing on the PDA a position of the laser rangefinder within the room.