# How can I achieve cm accuracy for x,y,z outdoors positioning

How can I achieve cm or less accuracy for x,y,z outdoor positioning contained inside a 100 meter cube (bigger the better but this is minimum). I do not care if I need external beacons/sensors or internal beacons/sensors I just want accuracy.

I suggested 100m cube to make the problem hopefully easier to solve. I can place beacons etc inside the cube.

Any ideas?

Thanks!

• Can you please be more detailed. Are you talking about GPS? One time to mark a point? Again and again? Position of a moving thing? What will you do? – Kitana Nov 26 '14 at 21:09
• In my experience GPS is just not accurate enough. If there is a way to do this with GPS with low  then that is awesome. Can I buy what I need from adafruit.com? If I can keep it under $500 that is great! – Jamey McElveen Nov 26 '14 at 21:13 • Hmm a laser range finder and corner cube reflector. (that gives a distance, then you need three angles.) – George Herold Nov 26 '14 at 21:14 • I am thinking of using this for a quad copter. I want to control it's movement very precisely. – Jamey McElveen Nov 26 '14 at 21:17 • I saw these guys at a trade show a few months ago: timedomain.com and they were demoing an ultra-wide-band pulsed-RF ranging system which allegedly achieved 2cm accuracy ... – brhans Nov 26 '14 at 21:56 ## 2 Answers Real-Time Kinematic carrier phase GPS can achieve centimeter-level accuracy. The Piksi system from Swift Navigation is the lowest-cost system that I'm aware of, approximately$1000 for a pair (you need one unit as a fixed base station).

I think the only realistic way to solve this without exotic (and expensive) components and subsystems is with cameras and machine vision. Still, that won't be easy, the image processing is not trivial, will require careful calibration, and 10 mm is still a bit too aggressive.

There are systems that work on this principle. One that comes to mind is motion capture from live actors. They usually wear special suits with reflective and sometimes emissive patches on them at key points like the joints. Each camera captures the 2D angle to a bunch of patches each frame, and some pretty fancy software on powerful processors pieces all these angles together to find the 3D location of the patches.

Again, I think 10 mm accuracy within a 100 m cube is out of reach, but perhaps it will still be good enough.

This method is complicated, expensive, and probably not accurate enough, but everything else will be even more complicated and most likely prohibitively expensive unless you're NASA or the military.

• Thanks! I actually considered this. I have a few old iPhones that I considered placing on the device and using markers and an open source library like opencv.org. My challenge is distance to marker and line of site. In theory this works but has a very limited range and requires a massive marker to achieve any distance. – Jamey McElveen Nov 27 '14 at 15:59