Hi, I’m using RealityScan v2.1 and I have a question about coordinate systems.
Workflow summary:
- I reconstructed a model from a set of drone images (with GPS) and the reconstruction looks good.
- I exported the mesh using the export coordinate option “Project output (EPSG:4326 - GPS (WGS 84)).”
- I also exported the point cloud but chose the “Grid plane” coordinate system for that export.
My question(s):
- What is the relationship between the same model exported in these two coordinate systems? In other words, how do coordinates of the same 3D point correspond when the mesh is exported in EPSG:4326 (WGS84) and the point cloud is exported in Grid plane?
- If I already know the 3D coordinates of points in EPSG:4326 (latitude, longitude, altitude), how can I compute the corresponding coordinates in the Grid plane coordinate system? What steps, formulas, or transformation should I apply?
- Is the mapping between EPSG:4326 and Grid plane an affine transformation (translation + rotation + scale), or is it some different kind of transform?
- Does RealityScan export or make available the transformation matrix or metadata that maps between these coordinate systems? If so, where can I find it (in exported files, metadata, or project files)? If not, what is the recommended workflow to align models exported in different coordinate systems?
Any pointers to documentation, exact formulas, or practical steps (or sample files/metadata to inspect) would be greatly appreciated. Thank you!
Hi @biabiabia66
You can check this article: Differences between exported coordinate systems in RealityCapture | Knowledge base
But I suppose there is no direct transformation between those systems, as grid system can be different (slightly) for each alignment.
Hi @OndrejTrhan, thanks for the clarification.
I’d like to follow up with one more question:
If there is no fixed global transformation between EPSG:4326 (WGS84) and the Grid Plane because the grid can vary per-alignment, then how should I interpret the relationship between the two coordinate exports?
More specifically:
If I export the same reconstructed model twice — once in EPSG:4326 (WGS84) and once in the Grid Plane — are the coordinates of the same physical 3D point still correspondable?
For example, if I know the latitude/longitude/altitude of a point in the EPSG:4326 export (as shown in the image), is there a recommended method to compute its corresponding coordinates in the Grid Plane export?
Or does the Grid Plane coordinate system depend on the internal alignment in such a way that the mapping is not reliably reconstructible from the exported data alone?
Just trying to understand whether the two exported representations can still be aligned point-to-point, and if so, what information or workflow is needed to compute that correspondence.
Thanks again!
Yes, they are the same. You can see the actual internal coordinates in the exported XMPs for example. There is the camera position in the internal coordinate system. When the project is georeferenced there are also shown the lat/lon coordinates. So, it is possible to transform such coordinates, but the transformation can be different for each alignemnt/project.
