Can't create grids in GM v19

Hunter GeophysicsHunter Geophysics Global Mapper UserPosts: 75Trusted User
Hi there,

Just upgraded to GM v19 (from v16), so I'm still coming to terms with all the changes made in the last few years.

I have imported an air photo from a drone of a cemetery, and have measured the width and length of one particular headstone using a measuring tape. I assigned one corner of the headstone as MGA coordinates 0,0, and then rectified the air photo using the headstone measurements.

While this isn't perfectly accurate, it's good enough for my current needs (and budget).

I now need to draw grids on the air photo. Unfortunately, when I go to do so, I get an error message saying "unable to project anchor point to lat/long" (even though my projection is set to MGA). Screenshot attached.

I've never rectified aerial imagery in this fashion before, but today is also the first time I've used GM v19.

Can anyone please suggest how I should go about doing this?

A copy of the GM project file can be found here.

Thanks in advance,

Best Answer

  • geomanniegeomannie Global Mapper User Posts: 208
    Answer ✓
    I think that your problem is that while you have selected a datum and coordinate system (MGA), your data are in fact set to an arbitrary origin selected by you. Your location bear no relationship to a true geographical location. Thus when GM says "unable to project anchor point to lat/long" it is simply being truthful. Your coordinates are not a true geographic location and GM cannot do the operation you want.

    Without thinking about this a bit more I cannot see a answer other than giving true coordinates (MGA or other) to your image.


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