Setting Scale

StarskyStarsky Global Mapper UserPosts: 6
edited September 2011 in Technical Support
Hi,

Is it possible to set your own scale in GM? I have an image which I don't have any know coordinates for and which I therefore can't georectify, it does however have a line feature on it which I know the length of. Is it possible to use this to set the scale for the image so that I can then measure other features on it?

Thanks.

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited September 2011
    You can't do that with a raster layer, but you could just fake some coordinates with a projected system in the desired units such that you get the desired length, then you should be able to measure as desired.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • StarskyStarsky Global Mapper User Posts: 6
    edited September 2011
    Thanks Mike, I'll give that a go and see how I get on.
  • StarskyStarsky Global Mapper User Posts: 6
    edited September 2011
    Hi Mike. I've had a crack at this but am still having a few problems I'm afraid...

    I used the Worldwide High Res Image, to get 2 control points the appropriate distance apart, i.e. the start and end vertices of a line feature the same length as the one I am trying to georectify. I then used these as "fake" coordinates on my own image, obviously aware that these asre only representative coordinates but that they should allow GM to rectify the image and me to then measure area / line features within it.

    However once I have added the Long /Lat coordinates for the 2 control points and clicked "OK". The image I am then given is for some reason inverted by 180degress and also the scale bar on the image still appears to be inappropriate, the image is approximately 15Km accross but the scale runs from 0-7000km.

    Any suggestions how I can correct this?

    Thanks again.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited September 2011
    What is your rectification projection set to? Make sure is the same as the coordinates that you are entering. Also if you have longitude values in the Western Hemisphere or latitude in the Southern Hemisphere enter them as negative. If it helps you can also send me a screenshot of your rectification dialog and I can see what you are entering.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
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