Global Mapper v25.0

Ohio NAD83 HARN to NAD27

jdm7102
jdm7102 Global Mapper User
edited March 2011 in Raster Data
I have noticed that when converting HARN to NAD27 the images are about 20 Meters off line. This forces me to go to ArcGIS and set the Geographic Transformations in order to convert the photos. Is there a way to set Geographic Transformations in the much more User Friendly Global Mapper to maybe Eliminate this step?

Thank you

Comments

  • global_mapper
    global_mapper Administrator
    edited March 2011
    How are you doing the conversion in Global Mapper? I would expect that conversion to be extremely accurate as both use grid shift files for the datum conversion.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • jdm7102
    jdm7102 Global Mapper User
    edited March 2011
    The steps I took were as follows.
    -Loaded the aerial into Global Mapper
    -Loaded the OHIO HARN NAD83 projection file because Global Mapper didn't automatically recognize it.
    -Set the configuration to change the projection to NAD27
    -Exported referenced Aerial and tested it in ArcMap, it was about 20 meters off.
  • global_mapper
    global_mapper Administrator
    edited March 2011
    If you load other imagery (for example DigitalGlobe imagery via the File->Download Online Imagery menu command) in Global Mapper does it line up with your aerial imagery prior to export? Are you certain that the data is originally in the Ohio HARN NAD83 projection and isn't already using NAD27 or some other datum?

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com