Global Mapper v25.0

Trimble jxl (xml), GM Transformation, Pix4D Arbitrary CoordSys.

Zoran
Zoran
in Projection Questions

Hi there, would be possible (to get GM) to read Trimble jxl and create/update custom Datum and projection? I've got some odd local system ... It seems that Pix4D offers set up of an arbitrary coordinate system with following parameters: X-translation, Y-translation, Z-translation, Rotation around X, rotation around Y and rotation around Z as well as scale factor.

image.png

where GM "transformation setup" is somewhat limited.

image.png

Thanks

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Answers

  • RonTheSurveyor
    RonTheSurveyor

    Late answer (not really) as I just stumbled on this post.

    How are you getting from Pix4D to JXL?

    Pix4d uses a coordinate system based on the first photo used. Origin is 0,0,0 at the centre of the camera, and one axis (don't recall which one) goes straight through the lens, the others 90° from that.

    The best way to convert it to some real coordinate system is to used ground control points with real coordinates. That's where your local friendly surveyor comes in handy. If you don't have that, you can create some fake ones using a method something like this:

    • If you have building corners or something in your model that you can see in Google Earth, you can click on them and get coordinates in some system. I usually use UTM. You will get elevations as well, but more on that below.
    • Create GCM points in your model at the same building corners, but make sure that they are at the same elevation. Follow a brick or roof line.
    • When you import the UTM coordinates of the building corners, make sure the elevations are all the same. This will prevent the model from tilting away from vertical.
    • After the model has been converted to UTM, you should be able to export the point cloud in UTM (or whatever projection you used) and bring it directly into GM.

    This will get you close, but not very accurate.

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