GPS like function - short range and precise

Hi Everyone,

Before I go to efforts to create such a system, I would like to know if anyone has come across such a system.

The requirements are to measure the position of a small mobile vehicle within a 50m by 50m area. Larger and smaller areas are also on the cards.
Precision to be 20 to 30mm (about 1 inch), measuring a 2 dimentional position. If it can measure depth, that would be a bonus. Base stations can be setup near by at fixed, known positions. There is no restriction on technology, including laser, radar, radio waves or sonic, as long as it does not harm anyone walking around it.

I have been keeping an eye out for something like this, although GPS seems to have flooded out the market.

Thanks,

Doug

http://www.locatacorp.com/
ground based GPS reletively new to market

There is also WIFI based systems Minesite Technologies, Northern Lights(NLT), Becker

Interesting......

I am picking through that web site to see what I can see.

Thanks Kellian

What else is located in the 50m 50m area? is it going to ruin line of sight
What locates the end of the area - walls ?

What about RFID?

There may be objects in the area, if so they will be mapped and the vehicle will avoid them. The borders may or may not be walls. Generally, it is assumed to be outdoors.
Line of site will generally be OK from all locations.

I'm finding it interesting looking up solutions - technology has moved since I last looked

Please tell up what you end up with

http://www.hexamite.com/hx17.htm

That hexamite looks interesting, may not do what I want now, but there may be something coming along that I could use it on.