For datasets acquired with DJI Phantom 4 RTK (P4RTK) we recommend the following workflow:
Creating a project
- (RTK) Image geolocation, horizontal and vertical accuracy is automatically recognized when importing the images.
- (PPK) After PPK postprocessing in a third party software, accurate image geolocation can be imported using the Image geolocation file (.csv, .txt, .dat). If necessary, edit the Accuracy Vert/Horz column to define the actual accuracy values.
- The optimized camera parameters for P4RTK (FC6310R_8.8_5472x3648) are already included and automatically recognized in the internal camera database.
2. Configuring the image coordinate system:
In the Image Properties Editor, change the vertical coordinate system to ellipsoidal heights instead of automatically detected geoid heights (EGM96). To do so:
- Open the Select Image Coordinate System editor.
- Click Advanced Coordinate Options.
- Select Geoid Height Above WGS 84 Ellipsoid.
- Click OK.
Edited on January 24th 2019
With the latest Pix4D Desktop 4.4.9 Preview version, the image vertical coordinate system is correctly detected automatically (WGS 84 Ellipsoid). With the previous versions, the above mentioned workaround needs to be applied.
There is no need to change the default processing templates, e.g. 3D Maps, and the following processing options can be kept:
Can I process with the accurate geolocation pipeline?
- Accurate geolocation and orientation pipeline can be used when both, image geolocation and orientation, are precise.
We recommend using it for large datasets (faster processing) and when the dataset contains homogeneous or complex visual content (forest and dense vegetation, flat terrain with agriculture fields, snow, sand, and water surfaces).
More in the FAQ on the accurate geolocation pipeline.
Is it possible to use another vertical datum besides EGM84, EGM96, EGM2008 or the ellipsoid of the selected horizontal system?
- There is no direct way of selecting or importing a different vertical datum.
A workaround is to either provide the offset between the desired datum and the ellipsoid of the selected horizontal coordinate system or select the option Arbitrary Coordinate System for the outputs and the GCPs and import GCPs with coordinates in the coordinate system you specified.
More in the When to use the Geoid Height Above the Ellipsoid Function? and How to define Pix4D outputs with respect to a Geoid model articles.
Do I need to enable the linear shutter optimization?
- More in the Phantom 4 Pro Rolling shutter effect community post.
What could cause a big offset when comparing the results with checkpoints?
The horizontal offset could be caused by the horizontal grid corrections and transformations.
In some cases, when flying fast, close to the ground or in high winds, enabling the linear shutter optimization could reduce the offset.
The vertical offset could be present due to wrongly selected vertical coordinates system or custom geoid models.
In case the optimized camera parameters are far from the initial values, e.g. focal length, we recommend using the All Prior processing option.
- DJI Phantom 4 RTK: next gen accurate drone surveys - Official Pix4D blog post.
- First look at the Phantom 4 RTK - User test by Michael Cutfield.