Surveying Device Time Synchronization for UAV Photogrammetry
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Solution Overview
Problem
Current photogrammetry systems face accuracy issues when using GNSS for UAV positioning, as it is less accurate than total station positioning, and cannot function in areas with obstructed GNSS signals, and require pre-defined reference points for image identification.
Innovation Solution
A surveying device that determines the position of a photographing device using a total station, which includes a photographing condition obtaining unit, time measurement unit, and photographing position analysis unit to associate survey results with image timestamps, generating data for photogrammetry without relying on GNSS or reference points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the position of the UAV is determined by the GNSS, then the survey can be conducted in open areas, but the position accuracy is less accurate than total station positioning
Solution Approach 1:
The patent segments the positioning function into two distinct systems: GNSS for providing photographing position information in open areas, and total station for providing survey position information in obstructed areas. This segmentation allows each system to operate independently based on signal availability, resolving the contradiction between position accuracy and signal availability by providing multiple positioning pathways.
2Measurement precision
If the position of the UAV is determined by the total station, then the position accuracy is improved, but the total station cannot recognize the photographing time and a time difference occurs between photographing time and surveying time
Solution Approach 1:
The patent implements feedback mechanisms where the photographing condition information (including photographing time) obtained from the photographing device is fed back to the surveying device. The time measurement unit measures time based on this feedback information, and the photographing position analysis unit uses this time-synchronized data to associate survey results with photographing positions, eliminating time differences between photographing and surveying operations.
3Measurement precision
If reference points are provided in advance in the target range, then the photographing position can be identified, but the system complexity increases and requires pre-preparation
Solution Approach 1:
The patent enables the surveying device to self-determine photographing positions by obtaining survey position information from the total station and associating it with photographing position information from the GNSS and photographing condition information. This self-service capability eliminates the need for manual reference point provision and reduces system preparation complexity while maintaining position identification accuracy.
4Ease of operation
If the total station is away from the camera during photographing operation, then the photographing operation can be conducted independently, but the total station cannot recognize the photographing time
Solution Approach 1:
The patent applies preliminary action by having the photographing condition obtaining unit obtain photographing condition information (including photographing time) from the photographing device before the photographing operation begins. This preliminary acquisition of time information ensures that even when the total station is away from the camera during independent photographing operations, the photographing time information is already captured and can be used for accurate association with survey results.
Data Source
AI summary
When a camera and a surveying device are connected by a synchro cable, and a photographing condition obtaining unit obtains a photographing start time of the camera, a survey control unit makes a survey time measurement unit start time measurement. After the camera and the surveying device are disconnected, the survey control unit starts a survey by a predetermined surveying period ΔT when tracking of the prism starts. Based on the time measurement by the survey time measurement unit, the survey control unit associates the survey result with the photographing position of each image taken by the camera to generate the data for photogrammetry.