location finder

Hi, I'm looking for a way to detect the location (in 3D) of an object with reference to another object. I'm looking for a solution that will be very cheap with reference to the receiver. The transmitter may be expensive, but the receiver must be cheap because I will need to have many (hundreds) of receivers and one main transmitter... Also this must be utilized over long distances. Can anyone help me out on a good medium? I can use 3 different transmitters to triangulate the location of the object. Thanks

3e4343

I don't wanna bust yur bubble, but GPS has already been invented.

but...

true... but that is too expensive for what i'm looking for... i need this to only work in a radius of about 1km... operation from a central source, can i say put up three antennas with waveguides so that they can transmit relative angles and the receiver can calculate the exact location from transmitted information???

Hi shaddy,

1 In order to locate a receiver in 3D you need at least 2 transmitters and preferably 3.
2 The receivers need to talk back to the transmitter location (or some other site) to report the time of clock signals reception from the transmitter.
3 Each transmitter and receiver must have a seperate ID code.
4 The transmitters must be synchronized to an extremely accurate time base.
5 GPS works worldwide within a tolerance of about 3 meters (depending on your equipment, location,etc.)