Global Mapper Pro

Transform GCP and Apply to Raster

anabranch Global Mapper UserTrusted User

I have processed some UAV imagery into orthomosaics and digital elevation models. I used the GCPs that we surveyed in the field using a dGPS. Unfortunately, after having processed all the data it was discovered that our GCPs were wrong by about 1.5m in the horizontal and 1m in the vertical. I do not want to have to reprocess the UAV data as some of the datasets took almost a week to run.

I have separate files with the incorrect and correct GCPs. Can I use the 'Transform Coordinates Based on a File' to get the Coordinate Transformation values that I can then use to transform the raster layers into the correct XY position? If so, what format do the GCPs need to be in? Currently they are csv files with Point ID, Date/Time, X, Y, and Z as the columns. Do they need to just be the XYZ values in txt or csv format?

For the Z adjustment I was just going to use 'Alter Elevation Values' in the Elevation Options tools that come up when right clicking on the DEM. Is that the best course or would the Raster Calculator be better?

Thanks for your help,

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