Re: Lat, Long, Alt conversion to X, Y, Z.

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ceti (ceti++at++worldnet.net)
Fri, 25 Oct 1996 09:18:54 +0100

>On Oct 22, 10:57am, Michael Campbell wrote:
>> Subject: Lat, Long, Alt conversion to X, Y, Z.
> convergance = cos( origin_lat * RADIANS_PER_DEGREE );
> /* compute this value once and cache it - it doesn't change */
>
> /* x,y,z units are now in _meters_ */
> x = (lon - origin_lon) * convergance * METERS_PER_DEGREE;
> y = (lat - origin_lat) * METERS_PER_DEGREE
> z = alt;

Ok If you don't search a real map matching with your 3D world and your DEM
this works and if the area is small it is as good and faster than other
mathematicals models.

But if you are searching the real match, you'll face problems that are the
geodethic earth model and the used projection.
( for instance , GPS is working mainly in WGS 84 that parsely fits with the
nautical maps, so you have to change its geodetic model for output)
This is a problem I've been already faced with, and you need a library to
cross convert your data. If you need more, I may help you for this because I
own a tool to do this.
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