In the first stage we installed GNSS base station on the point with known coordinates and measured locations in RTK mode of six ground control points distributed over the survey area. (Pic. 1, Pic 2).
Pic.1 Topcon GR 5 GNSS base station
Pic.2 Ground control point
In the second stage a drone mission was planned (Pic.3) , uploaded to DJI PHANTOM 4PRO GNSS RTK/PPK (Pic. 4). The flight mission was performed with the following parameters:
- survey area 40 hectares
- flight speed 10 m/s
- overlap 80/80%
- altitude 200 meters above ground level.
Pic. 3 Location of the survey area and flight routs
Pic.4 DJI PHANTOM 4PRO GNSS RTK/PPK
Stage 3. Photogrammetric processing. After landing, GNSS data were download from the drone via wi-fi and RINEX files from drone and base station were processing together using RTKLib postprocessing software (Pic. 5.). Differences between images locations measured by standard DJI GPS and upgraded GNSS system are shown at Pic.6
Pic.5 GNSS post processing report
|
GPST |
latitude(deg) | longitude(deg) | height(m) | Q | ns | sdn(m) | sde(m) | sdu(m) | sdne(m) | sdeu(m) |
sdun(m) |
|
10:30:57.823 |
55.42721116 | 37.09866392 | 383.2712 | 1 | 13 | 0.0077 | 0.0049 | 0.0148 | -0.0034 | -0.0043 |
0.0067 |
|
10:31:01.823 |
55.42692354 | 37.09902841 | 382.1284 | 1 | 13 | 0.0077 | 0.0049 | 0.0148 | -0.0034 | -0.0043 |
0.0067 |
|
10:31:05.823 |
55.42663183 | 37.09938321 | 380.809 | 1 | 13 | 0.0077 | 0.0049 | 0.0148 | -0.0034 | -0.0043 |
0.0067 |
|
10:31:09.823 |
55.42634191 | 37.09974165 | 379.716 | 1 | 13 | 0.0077 | 0.0049 | 0.0148 | -0.0034 | -0.0043 |
0.0067 |
|
10:31:13.923 |
55.42604749 | 37.10009267 | 378.2999 | 1 | 13 | 0.0077 | 0.0049 | 0.0148 | -0.0034 | -0.0043 |
0.0067 |
|
10:31:18.123 |
55.42575137 | 37.10045163 | 376.7581 | 1 | 13 | 0.0077 | 0.0049 | 0.0148 | -0.0034 | -0.0043 |
0.0067 |
|
10:31:22.222 |
55.42546214 | 37.10080242 | 375.5348 | 1 | 13 | 0.0077 | 0.0049 | 0.0148 | -0.0034 | -0.0043 |
0.0067 |
|
10:31:26.422 |
55.42516381 | 37.10116678 | 374.3488 | 1 | 13 | 0.0077 | 0.0049 | 0.0148 | -0.0034 | -0.0043 |
0.0067 |
Pic.6
Photogrammetric processing was carried out in Photoscan software. Precise coordinates of image position were imported to the project and used for images alignment. Coordinates of ground control points were necessary only for the model accuracy estimation.
The following results were achieved with using precalibrated parameters of focal length F=3642.97108 and GPS offset Z=-0.21. (Pic.7,8,9)
Pic. 7
Pic. 8 Accuracy of image locations
Pic. 8 Accuracy of GCP location
|
#Label |
X/Longitude | Y/Latitude | Z/Altitude | X_error | Y_error | Z_error |
|
gcp1 |
37.108468 | 55.428252 | 177.5342 | 0.095565 | 0.116266 | -0.155084 |
|
gcp2 |
37.105661 | 55.429969 | 185.2419 | 0.060218 | 0.108619 | -0.057785 |
|
gcp3 |
37.104604 | 55.42775 | 187.5888 | 0.053902 | 0.033637 |
-0.117375 |
| gcp4 | 37.101668 | 55.430107 | 192.0927 | 0.025702 | 0.060954 |
0.020079 |
| gcp5 | 37.101818 | 55.425095 | 191.8068 | -0.048562 | -0.088709 |
0.086965 |
| gcp7 | 37.098997 | 55.427386 | 192.1309 | -0.051945 | 0.01491 |
-0.073903
|
The results of the project shows capabilities to use a low cost DJI PHANTOM 4PRO upgraded with GNSS RTK/PPK receiver as a survey grade UAV. DJI PHANTOM 4PRO RTK/PPK provides high accurate drone data for precise mapping and 3D modelling. You no longer have to lay down GCPs or just minimize their number, saving countless hours and labor costs.
https://cloud.mail.ru/public/LcUW/aPGxNnehc