By Tersus GNSS
The Tersus Post-Processing Kinematic (PPK) and RTK systems are dual frequency GPS/GLONASS/BeiDou receivers. They allow cm-level position referencing of orthomosaic photos and 3D models without the Ground Control Points (GCPs). It saves hours of mission planning and setup time for surveying.Read more
When using the Aerial Surveying with GNSS RTK PPK System, you typically set the BX306 into the PPK mode, despite the BX306 can output the real time kinematic results. In such mode, you can eliminate the datalink between the airplane and base station.
All GNSS positioning data are stored on board in the BX306 PPK system, without a real-time data link with reference station. The BX306 connect with hot shoe with the camera, we could get camera cm-level locations during the post-processing procedure after flight. The corrected image positions are directly added to the image EXIF and can be imported to photogrammetric software packages such as Pix4Dmapper or Agisoft Photoscan.
The objective of the test is to validate the accuracy and precision of the BX306 PPK solution.
Figure 1 Connection of the BX306 with camera
2 Survey Area
The test site is located in Shanghai of China.
Figure 2: Location map
2.1 Information about acquired data
In parallel the BX306 receiver records the shutter events of the camera and logs the GNSS raw measurements information during flight on an on-board memory /SD card.
TY-M400 PPK drone carried the Sony A6000 camera with a 16mm wide angle lens providing a nominal Ground Sampling Distance (GSD) of 2.34cm at 120 meters.
4. Data Collection and Processing
The accuracy of UAV PPK system is validated by comparing the results of aerial surveys with precisely measured verification points (GCPs). The verification workflow includes following steps:
4.1 Surveying the Control Points
The majority of the control points were selected in the crosswalk line and it was very easy to find. All points were measured by a Tersus David GNSS survey grade device using RTK corrections from local QXZW VRS. The ground survey produced a horizontal accuracy of 8mm and a vertical accuracy of 10mm.
Figure 3: Tersus David GNSS Receiver
Figure 4: Surveying the GCPs
Figure 5: Position of the GCPS Surveyed by surveyor
Figure 6: GCPs
4.2 Reference Base Station
The PPK does not need a real-time data link with a base station during a flight. However, GNSS raw data has to be recorded by base station in rate 1HZ. (We set the BX306 in the drone with 5HZ refresh rate)