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RobA
07-28-2008, 02:57 PM
I wanted a utility the other day, and couldn't find it...

I'd like to be able to load a rectangular map (equirectangular, or not) image, and specify the latitude and longitude of the four edges (in the case of a full world equirectangular mapping, that would be +90, -90 (north to south) and +180, -180 (east to west)) and the planet radius/diameter in "units".

Now let the user pick zoom in/out and pick any two points, to calculate and display the great circle distance (http://en.wikipedia.org/wiki/Great-circle_distance)

If I had a programming environment more recent than VB3.0, I'd try putting this together my self :) 'cause I don't think it is too complicated.

-Rob A>

jfrazierjr
07-28-2008, 03:06 PM
Rob, you can actually download a lite version of VisualStudio if your interested and no one else beats you to it first.

Joe

waldronate
07-28-2008, 04:51 PM
FT will do what you're asking, I think.

1) Load the map as an image overlay (equirectangular only, but ReprojectImage at http://www.ridgenet.net/~jslayton/ReprojectImage.zip will convert the projections)
2) Zoom and pan to get the desired area(s).
3) Use the ruler tool to measure distances (it does great circle distances).

If you don't have a retail copy of FT then you can download the demo from ProFantasy. It won't export things at high resolution or save things past the initial demo period but it will still measure things even after it's expired.

waldronate
07-28-2008, 04:54 PM
As an aside, I like the Aviation Formulary for general great-circle computations. http://williams.best.vwh.net/avform.htm gives the forumulae that you'll want ot know for general navigation on a spherical earth. It's quite similar to navigation on an ellipsoidal earth, but the 1 part in 300 deviation isn't usually that important unless you're trying to enter a harbor or not fly into a mountain or suchlike.

su_liam
07-29-2008, 02:18 AM
If java works for you, I should be able to put something like that together for you. Hopefully the deadline isn't too short...

RobA
07-29-2008, 01:57 PM
No rush at all. I currently work around using google earth, but then have to multiply the displayed distance by the ratio of the new world to earth (diameters).

-Rob A>