Precise distance sensor for upto 15 meters

Hi,
I need a distance sensor that is fairly precise (say 5%) and that can give me the distance upto 15 meters (i need to detect the distance
between a mobile robot and a object that can be upto 15 meters away). I don't need a wide angle (the smaller the angle, the better).
Should I use ultasonic sensor ? Or laser beam ? How much will it cost me ?
Alok.
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Depending on the system (like the older Polaroid transducers) sonar can be used to up to 35 feet (about 5 meters), but that's "on a good day." Wind, humidity, and temperature can seriously affect the accuracy of sonar distance measurement, even the high-end stuff.
Laser is certainly an option, but can be fairly expensive. Radar is another possibility, and may be cheaper.
Prices for these types of sensors start at maybe $100, to well over $5,000. The difference is durability and accuracy. Instead of going back and forth to find what you're looking to pay, why not give us a ballpark figure. It'll be easier to provide answers that way.
-- Gordon Robots for Less at Budget Robotics: http://www.budgetrobotics.com/ Author: Robot Builder's Sourcebook & Robot Builder's Bonanza
Alok wrote:

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Ok, thanks for the info.
What is the difference between a radar and a sonar (is it only the frequency of the signal) ? Do you know what cars use on the back bumper to help in parking ?
Alok.
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I have one of those "Park Zone" parking indicators in my garage (I need to park with my back bumper as close to the garage door as possible). It uses sonar and it is very accurate. It picks up the vehicle about 15 feet from its location and I stop about 3 feet from the unit. As long as I slow down when I'm close and hit the brake right when the red light comes on I seem to stop within less than an inch of the target location. Much of that error is probably due to timing hitting the brake.
I know these distances are less than what you are talking about, but I thought you might find this info interesting.
Bob

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