Global Mapper v25.0

Coordinate convertor problem

rbr
rbr Global Mapper User
edited December 2008 in Projection Questions
Hi,

I have converted, with the global mapper coordinate convertor, the following value between geo( lat-lon) wgs84 datum to
mercator kkj datum:

27.07400521861
61.6390009939 in geo( lat-lon) wgs84

converted to mercator /kkj is

3014341.442
8736525.795

This conversion seems to be incorrect. In fact, using the conversion system provided by the Finnish institute at this link:

Citizen’s MapSite - National Land Survey of Finland

I have a different result.

Could you help me understand why?

Comments

  • global_mapper
    global_mapper Administrator
    edited December 2008
    The Finnish Grid system is not a Mercator projection but a Transverse Mercator with the following parameters:

    Transverse Mercator
    DATUM: KKJ (FINNISH GRID)
    UNIT: meters
    CENTRAL MERIDIAN SCALE FACTOR: 1
    CENTRAL MERIDIAN: 27.000000
    ORIGIN LATITUDE: 0.000000
    FALSE EASTING (m): 3500000

    If you use that you should get results that agree with the official conversion site.

    Note that I did take a look at the datum conversion and find slightly better parameters than were used that should give you sub-meter accuracy in the conversion. I have placed a new build at http://www.globalmapper.com/global_mapper10.zip with the change for you to try. Simply download that file and extract the contents into your existing v10.xx installation folder to give it a try.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • rbr
    rbr Global Mapper User
    edited December 2008
    Thanks,
    everything is fine now.

    Best regards.