Global Mapper v25.0

Datum Parameters

PatG
PatG Global Mapper UserTrusted User
edited November 2009 in Technical Support
I have a Local datum setup and saved based on the GRS80 ellipsoid with a TM projection.

The parameters for GRS80 are:
Semi Major = 6378137.0
inv flattening = 298.257222101

These are stated in the GlobalMapper ellipsoid file (ellipsoid.csv)

However if I save my datum to a file it states the following for GRS80

SPHEROID["GRS 1980",6378137,298.2572220960423]

Why the discrepency and how much will it affect my translations?

Cheers for any info....

Comments

  • global_mapper
    global_mapper Administrator
    edited November 2009
    Pat,

    The ellipsoids.csv file does not contain the ellipsoid definitions used by Global Mapper, it is a data file used by one of our 3rd party import libraries. The difference in the flattening value is extremely small and would result in differences less than 1 mm in size.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com