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Dark GDK / Map from data

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freight dog
16
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Joined: 12th Aug 2008
Location: Probably in a airplane
Posted: 11th Jun 2009 09:36
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Ive been wanting to tinker with gps mapping to write my own system for use at work.(aviation)

Basicly I have waypoint data in the format of

fix lat long alt
klax, somlat,somlong,somalt


Anyone have any ideas on how to convert those lat/long to x/y and draw a map with it so far I havent been able to find any examples for doing this on this site or across the web

Thanks
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AlexI
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Posted: 11th Jun 2009 21:05
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Cant you just use the same scales?

1)Load the points
2)Create a sphere for each point
4)Join points with a box or something
3)Set the camera range to a suitable number
4)Set Camera position at a suitable distance above the points


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Mireben
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Posted: 11th Jun 2009 21:14 Edited at: 11th Jun 2009 21:17
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If you work in aviation, then you know that several different map projection algorythms exist. I suppose the most often used is stereographic projection.
I would say search for "stereographic projection" and see if you can find a site with formulas which you understand. (I once tried to understand that method, but gave up quickly.)

P.S. Alex, I think his problem is not how to present the points, but how to calculate X/Y from lat/long which is far from easy.
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AlexI
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Posted: 12th Jun 2009 01:16
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Quote: "P.S. Alex, I think his problem is not how to present the points"


Oh


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kklouzal
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Posted: 12th Jun 2009 02:29 Edited at: 12th Jun 2009 02:33
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Could you not get a large FLAT 3d model of the earth, then from that take the top left corner of the map and make it x = 0, y = 0, lat = 0, lon = 0(or whatever the approaiate values are), then from there figure the bottom right lat/long numbers & then do some algebra and figure how x&y can move accross the 3d plain at the same rate lat & lon would? It makes sense to me >.<

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Mireben
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Posted: 12th Jun 2009 08:10
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One more thing. If a simplistic approach is enough for your purpose, you could cheat a bit and suppose that the distance between lat/long lines is constant (which is not true in reality) and make an easy linear calculation. This works as long as the displayed area is small, because the curvature of the lat/long lines is not noticable over small distances. But the mention of aviation made me cautious of recommending this. It's OK for a hobby project, but if the program is going to be used for a professional purpose, you probably need a more professional method.
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freight dog
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Posted: 12th Jun 2009 23:43
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Thanks
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