Global Mapper v25.0

Warped Image after reprojection?

DC-9
DC-9 Global Mapper User
edited August 2007 in Raster Data
Hi All,

Just curious if anyone could tell me why after I reproject my geotiff files, they appear to be distorted? I'm reprojecting from NAD83 to WGS84 datum with the Geographic Lat/Lon projection. Is there some type of setting I am missing? Thanks!


Mike

Comments

  • global_mapper
    global_mapper Administrator
    edited August 2007
    Mike,

    What is your original projection before you go to Geographic? Note that the Geographic projection will be distorted longitudinally (i.e. stretched from left to right). This distortion gets progressively worse as you near the poles.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • DC-9
    DC-9 Global Mapper User
    edited August 2007
    It was in NAD83. I'm reprojecting it to the WGS84. Is that the reason? Can this be avoided? I noticed that you can not keep the same units such as meters, and can only use arc seconds, etc. Can you still keep it in meters while using the WGS84 lat/lon projection?


    Mike
  • global_mapper
    global_mapper Administrator
    edited August 2007
    NAD83 and WGS84 are datums, not projections. It sounds like you are going from some projected coordinate system, like UTM, to the Geographic (lat/lon) unprojected system. Just keep your projection the same and change the datum from NAD83 to WGS84 (they are actual identical datums, so the change is in name only anyway) to keep the data un-distorted.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com

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