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[Closed] Why can't a GPS work out altitude ?

MidlandTrailquestsGraham · 2013-07-08T07:03:29Z

A GPS uses signals from satellites to calculate its position on a sphere* (the earth). If the satellites are orbiting the earth, the position must be worked out in 3D, not just 2D like triangulation. So, why can't a GPS work out altitude above the base line of the sphere as well as position on the sphere ? Why do GPSs always use barometric pressure to estimate altitude ? *Yes, I know it's not really a sphere, but it's very close.

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CountZero

Posts: 34016

Full Member

I'll certainly concede that altitude lost/gained may well be open to all sorts of cumulative errors while the device, whatever it is, tries to maintain its contact with the satellites. It's different to standing in one spot while the device settles down. Putting barometric sensors into phones/pads would be a useful addition, seeing as how they're being used more and more for outdoor pursuits where accuracy is needed.

Posted : 10/07/2013 6:49 pm

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