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Help:Determine location of a device??

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abicash

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Hello

I need some ideas for a concept i will elaborate.

There is a floor say 10,000 sq.ft. On this floor, multiple devices are scattered.
How to design something which would show the exact location of the device on a central location?

My idea was to use a GPS, but since the floor is covered (not open to sky) , this idea becomes outcast right away.
Next i thought of installing a network of RF Transceivers on the floor, and on the device and determine the location with interpolation. But there is a limit to this scheme since these would be only allowed to be installed on the edges of the floor.

Can someone think of something brilliant to solve this puzzle?

Thanks for reading
 
the fact you are indoors does not nullify gps.
you could put transceivers on the edges of the floor, and interpolate the results. Previous to gps, these systems were in use in the U.S.: Omega and Loran. They worked basically the same: Each system has a master transmitter, and a minimum of two slaves. The master transmits a signal. When a slave receives the master signal, it then transmits its signal on a different frequency. By bouncing the received signals off each other relative to the time of arrival at the ship, you can interpolate your posititon. The difference between Loran and Omega, is for the Omega system, we would get charts overprinted in their frequencies for the area we would be operating in. The receiver would give us numbers on the slave channels, and we would chart our positions using the overprinted charts. Loran, however, gave us a readout of lat and long directly (newer system). Problem: worked great during the day, gave us a nice little triangle for a fix, and as dusk approached the triangles would get bigger and bigger until we could tell we were somewhere in the Caribbean... now, these transmitters covered thousands of miles. You are only covering hundreds of feet. Radio waves (and light) travel at 1 foot/nsec. That means with 100 feet differential, you'd have signals 100 nsec, or .1usec (yes, that's a tenth of a microsecond) apart. Can you measure that accurately? You'll get some big triangles. I suggest for this type of system on this scale sound would be a better selection.

gps? gps is only accurate to 10 feet on a good day. Of course, all receivers would have the same error, so if you have a receiver at your central location, then all fixes would be relative to that central location.
 
Hello Mike

Thanks for replying.
The information is interesting but seems ineffective as per your defined limitation.

I just took a look on electro-tech and i found out few interesting threads.
One of them led me to http://www.rfctrls.com/

This uses Active RFID technology.
Is there a way this idea can be generated on an embedded platform - using microcontrollers?
 
How big are these devices, what resolution do you need, are they moving or stationary, how much money do you want to spend or is this concept only?
Does each device have a power source if so how big, are there other objects in the room which might obstruct line of sight measurements.

If the devices are moving and you have a known start point you could use inertial navigation ( gyroscopes and accelerometers to work our how far and in which direction you've travelled) they use this in UAVs to supplement GPS.

OR

You could have fixed reflective fixed reference points on the walls of the room, each device would then measure its distance to the reference points using a laser range finder and calibrated two axis actuator. With this information you could calculate each devices position.
I knew some guys at university who tried this type of thing but with microphones trying to triangulate a sound source - it worked but only in very quiet environments.

OR

If your looking for a low resolution measurement then RF 'fences' under the carpet / floor could indicate to the device when they have entered or left a certain part of the room.
This has limitations on resolution clearly but you have enough information to say, 'two devices are in the top corner of the room' '1 device is in the middle of the room'

OR

You could use swarm intelligence, colour each device differently and a camera on each device can then inform you 'device 1 is in front of device 3 but device 3 is to the left of device 4' With enough of this information you can build up a fairly good picture. With some short range collision sensors you could even get the swarm to create a 'crowd sourced' map of the room.

And finally,

Use a Kinect Sensor plugged into a micro computer, one on each device will defiantly work or alternatively having the Kinect sensors on the walls might work.

In short there are a lot of ways you can do this, you'll have to answer the questions at the top of this in order to know which one is right for you.
 
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