How do I convert a mobile phone GPS to x,y,z with origin at the center of the Earth?

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How do I convert a mobile phone GPS to x,y,z with origin at the center of the Earth?

I need to accurately visualize points coming from iPhone (and other) GPS data in 3D.

So, what I'd like is to take a WGS84 (right?) point and transform that into an X,Y,Z vector with the origin at the center of the Earth.

I Googled for GPS/WGS84 to 3D but I think my search terms are not so great

Does someone have a pointer for where to start?

In future, I'll also need to take elevation information into account if available, but that isn't so important immediately.

Thanks!

what your looking for is representing your data in ECEF (Earth Centered Earth Fixed) notation.

Some good wikipedia stuff

paquetp 2010-08-03 16:27:25

And here I was hoping we'd get an answer which included specifying the location of Earth within the universe :P

Brian S 2010-08-03 16:30:29

Wonderful, thank you Sir!

octonion 2010-08-03 17:11:33

Latitude and longitude are relatively easy, since they're just angles, however altitude is a bit tricky because the Earth isn't exactly round. If you don't need very great accuracy, this Wikipedia article has formulas for converting from a spherical coordinate system into a cartesian one. Be warned that this is not quite accurate because the Earth resembles an ellipsoid more than a perfect sphere.

Matti Virkkunen 2010-08-03 16:36:23

ECEF uses the ellipsoid model...see my answer if you need that much precision.

paquetp 2010-08-03 16:47:57

@paquetp: Oh, on second look, the article actually had links to some formulas at the bottom. Didn't notice that at first.

Matti Virkkunen 2010-08-03 16:52:51

Ah glad you discussed that. I was thinking it probably wasn't as easy as simple polar to cartesian.

octonion 2010-08-03 17:15:09

ansaurus

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How do I convert a mobile phone GPS to x,y,z with origin at the center of the Earth?

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