1. ## Global Positioning Metric

We have latitute and longitude, is there a measurement for how far off the Earth's surface we are, such as I am on the 10th floor? I know we can say 10,00 feet, but is there a 3-D coordinate?

2. ## Re: Global Positioning Metric

height from the see surface? or height from the surface? (these are used in plane navigation, so I can name them as fairly objectively practical and registered ones)... But maybe there are other kinds too. For example height from the earth center?

3. ## Re: Global Positioning Metric

But I want consolidated units.

4. ## Re: Global Positioning Metric

X, Y, Z?

You mean you need the height be of the same nature of the X and Y?

If so i think it is not possible in euclidean geometry, since X and Y are actually curves in euclidean geometry (they are lines spanned on the surface of a sphere), but Z here is a straight vertical line. So we will need non-euclidean geometry for that combination...

Or we can ignore the small error converting the curves into fake straight lines produce, and say we have a X, Y, Z system, all in metric units.

I guess the former is used in GPS, while the latter is used when reporting to the end-user the location (since the user doesn't care about those calculations). If you yourself know the answer, i am so curious to know.

5. ## Re: Global Positioning Metric

You may wish to investigate the World Geodetic System. I believe the most current version is WGS 84. This is the basis of GPS. Unfortunately, I have no expertise to offer beyond knowing the name of the system

John

6. ## The Following User Says Thank You to SmoothJohn For This Useful Post:

hlsmith (10-05-2012)

7. ## Re: Global Positioning Metric

This might help. As smoothjohn said most GPS's are based on WGS 84 and use a know base station coordinate for the z value, but as this doc. suggests, it is not always known what they are using. in this guide, it helps you calculate this.

http://homepages.slingshot.co.nz/~geoff36/datum.htm

8. ## The Following User Says Thank You to bugman For This Useful Post:

hlsmith (10-05-2012)

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