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I am doing the project with my friend. So, in this project every vehicle has a transmitter & receiver. Considering a particular vehicle we need to locate how many number of vehicles are there in its surrounding ( In the transmitter range ) along with the angle ( direction ) with respect to the car from which we are looking..

My friend was speaking about using radar.. he wants it to be installed in the system so that we could get this task done..

What I want to know : 1. Is this a possible solution? If not what else we can do to get this job done. 2. How much approx is going to cost for a small range Radar? 3. Suppose, there are 2 different vehicles separated by a distance of 10-20 cm in a traffic Jam.. can the radar show them clearly on the display / it will over lap the points on the display..

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closed as not constructive by Leon Heller, Kellenjb, Kevin Vermeer Nov 12 '11 at 16:15

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2 Answers 2

Radar is not what you want.

Radar involves sending out a signal and watching for the reflection of that signal off an object.

What you are looking for is more of a triangulation system.

There's 2 ways I can see of doing this:

  1. A rotating parabolic dish. This will give the strongest signal response when pointing directly towards the transmitting object. I'm sure you've seen these in cheesy 60's sci-fi movies.

  2. Multiple aerials and receivers. A signal sent from one point will arrive at different points with different strengths and at different times. Having receivers at different locations will allow you to triangulate where the signal came from. The further apart the receivers are the better the accuracy will be. Ideally you want a minimum of 3 receivers. Using 2 you will be able to cover a 180 degree arc, but you won't be able to tell which side of the line joining the two receivers the signal is coming from. A third, making a triangle, will give you the full 360 degrees.

While it would be possible to use multiple receivers on a vehicle, the distances between them will be relatively small, so the differences in signal strength and timing will be minuscule, and very very hard to calculate accurately.

A much better system would be to have each vehicle have a GPS module so it knows exactly where it is. It can then broadcast its location to vehicles around it so they then know where it is.

This kind of system is already in use in Swedish (and probably others') military (and I think some civilian) aircraft.

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Instead of the vehicles (cars on a road?) determining their relative positions to each other, how about each vehicle finds its own absolute position via GPS, then reports that? Now you just need radio telemetry links instead of distance measuring.

You don't say how accurate the positions need to be or how fast they need to be known, so sharing GPS coordinates over the cell phone network to a central server at a fixed location seems to fulfill your requirements. That will be a lot easier than doing your own distance measurements. Using radar may also not be legal without license, which is likely hard to get.

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This seems to be a nice idea. –  0cool Nov 11 '11 at 14:57
    
Yes, I am speaking about cars on roads.. so, noting coordinates is not really a possible thing because.. cars will not be at a particular location. –  0cool Nov 11 '11 at 14:59
    
I am googling on this topic.. and I got a tail to look at.. "Ad-Hoc".. what exactly is it and how could I implement it –  0cool Nov 11 '11 at 15:00
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@ocool: How is noting coordinates not possible? This is what GPS units do. As each car moves, it has to report its updated coordinate to the central server, which can then pass this information to other cars in the vicinity, which can calculate the relative positions. I can't understand why you think this is not possible because the locations are not fixed. –  Olin Lathrop Nov 11 '11 at 15:51

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