I'm interested in studying people's movement over time (24 hours), and would like to do so with devices that also measure elevation very accurately. I understand there's stuff out the where I can buy these for about $20 a piece, as I need about 30 of them. The data will be used in arcgis. Can someone recommend a specific brand to buy?

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  • I think you'll be hard pressed to find something that measures elevation "very accurately" and costs $20. Have you done any research on brands? – Paul Sep 4 '13 at 2:48
  • By "very accurately" I mean down to about 1 meter or so. I just need cost efficient GPS trackers that I can clip to a person's backpack or whatever. Ideas??? – Jeff Sep 4 '13 at 3:23
  • We'll be a little more apt to help you if you show that you've researched brands, constraints, etc. Google around a bit and narrow it down some. – Paul Sep 4 '13 at 3:30
  • They aren't accurate down to 1m, but what about just using mobile phone GPS apps? – RyanDalton Sep 4 '13 at 4:26
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    alibaba.com/product-gs/582488366/… is $22.8 to $24.5 depending on the number of units purchased. – Mapperz Sep 4 '13 at 19:57

The problem is that GPS usually have more uncertainty in altitude usually 1.5 times more than the uncertainty in latitude and longitude. The accuracy is normally +/- 23 meters, take a look to Joe Mehaffey's post in this site for a more detail explanation. Barometric altimeter usually have an accuracy of about 3 meters if properly calibrated. Modern device coupled both tecnologies to keep barometric altimeter calibrate with the temperature and barometric data for a specific position acquired from sattellites. Take in account that as Garmin says:

"GPS heights are based on an ellipsoid (a mathematical representation of the earth's shape), while USGS map elevations are based on a vertical datum tied to the geoid (or what is commonly called mean sea level). Basically, they are two different systems, although they have a relationship that has been modeled."

With twenty dollars I think that the only thing that you can do is to buy an app like Ultra GPS logger and eventually compare the data with a topographic map. If you want to know the floor in which your human cavia is, maybe you should think another approach: if you you plot the data of an accelerometer when you go up stairs you should see a series of waves. Of course you can see them even when you go down stairs so you should work to differentiate this two process. Coupled all things together maybe you can have what you want.

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