I was banging my head against this all day, perhaps someone knows how this is done: I have a building project that I am doing in Gmax, and I wished to get the building footprints very correct. So, I created a ground bitmap with 0.5m / pixel satellite imagery through FSEarthTiles, sliced a 1024 x 1024 chunk from it, and applied it to a 512 x 512 sized plane in Gmax, which I can then use to size my buildings' footprint.

 

Everything works fine, but after a bit of comparison, it becomes clear that the image isn't scaled quite right... So I carefully measure building footprints on my image from within Gmax, and compare my measurements to Google Earth, using the maps lab ruler. The measurement in the x (longitude) dimension is within a close enough tolerance, but the measurement in y (latitude) is quite a bit off.

 

So, after much mucking about with math, converting the degree measurements of my chunk of imagery to meters based on the latitude, and generally trying to figure out Mercator projection within FSEarthTiles, I was able to resize my chink of imagery in Photoshop to match a real world scale of meters in both dimensions. Or so at least I think...

 

Long story short - is there a better / generally accepted way to do this?? Bear in mind that the imagery is only for reference in creating the buildings, it will not be used in the resulting scenery.

I think you are right, you need to reproject your image.  In the US I would probably use State Plane Coordinate System, though I suppose Universal Transverse Mercator works just as well.  I use a payware GIS to do this sort of thing but I think there are freeware tools that can do it (command line or with GUI).  (FWTools maybe?)  Sketchup has the ability to directly import from Google Earth.  I'm not sure how it does it but maybe it reprojects while doing it. 

 

scott s.

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Googles states:

 

The coordinates, elevations, distances, and measurements provided by Google are approximations only. Google makes no
claims as to the accuracy of these measurements.