merge control points into a DEM

pg1974pg1974 Global Mapper UserPosts: 1
i'm trying to load such control points (contained in a CSV file) into a DEM. But i don't want to triangulate the control points first (by GRID-create elevation grid) otherwise the  heights  within the triangle could cause, in the merged file, false heights. I would like the DEM is integrated with the control point by modyfing just the height of the DEM where a control point is located. Is there any changes to do it?
thanks in advance for your support


  • geomanniegeomannie Global Mapper User Posts: 152Trusted User
    If I understand correctly, you have the following

    1. a grid file with values arranged in a regular grid (nodes)
    2. a csv file with control points that may or may not lie on the gid nodes.

    This is a well known problem in gridding but and I don't think that GM allows sufficient gridding options to provide an exact solution. I may be wrong. The following may, however, work.

    1. Open your grid into GM and then export as an xyz grid.
    2. Open the xyz grid into a suitable text editor (e.g. Excel, Openoffice Calc) and append your csv control points to the data table. Colour code your csv points so you can tell them from the grid nodes.
    3. You will need to sort the data by location and see if any of your csv points are identical to the the grid nodes. If so, delete the grid node points.
    4. Save the file and use the "Open generic text file" command and select the option "elevation grid from 3D point data".
    5. The resulting grid should approximate to the original grid modified by the control points.

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