Global Mapper v24.0

Adjust DEM to control points?

mcweb
mcweb Global Mapper User

Is there a way to compare/adjust a DEM to multiple field collected control points?

Similar to the LIDAR QC COMPARE ADJUST command, except - instead of comparing/adjusting a point cloud, it compares/adjusts a DEM.

Answers

  • 946
    946 Global Mapper User Trusted User

    What you can do is export your DEM to a laz point and after use the LiDAR QC as you already mentioned.

    After that recreate your DEM file.

  • Treebeard
    Treebeard Global Mapper User Trusted User

    if you grid both data sets (you might use the tightness slider to get a grid just near your actual points, you can then use the File->Combine Terrains menu command to combine the terrains into a new one with the difference between the layers.

  • Import your CSV.

    Copy the "elevation" attribute to a new attribute (I use "observed" for field collected elevations)

    Select all your points, right click, analysis, then update your elevations from the DEM (which will overwrite your ELEVATION field)

    Then copy the updated ELEVATION attribute to a new attribute (I use "predicted" for DEM elevations)

    Then calculate the Delta = observed - predicted.


    Converting to LAS and using the built in lidar qaqc is an option as well, but they function a little differently (and I don't want to do a rubber shit correction. I do a Z shift / Z bump).

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