I'm trying to build a device that can measure long distances(around 60 feet) I've considered sonar but am wondering if there are any better alternatives. Any suggestions?
Maybe something like this?
http://letsmakerobots.com/node/2651
Note that as the project stands, it won't work out to 60 feet - but maybe you could improve upon the general design?
so are you suggesting using a laser sensor? I would be detecting large objects around the size of a car.
laser can blind people (temporary)
Must the measurement be wireless? tell us more about what you want to accomplish for better ideas 
robtillaart:
laser can blind people (temporary)
Not at the 5 mW and under level that the device I posted uses, unless you trained it right at a person's eye; given that it is being scanned rapidly (much like a barcode scanner), that reduces any possible danger even further. If there is a worry about the scanning mirror stopping, build in failsafes for that if needed.
Most commercial laser distance scanners (SICK, Hokuyo, etc) use 5 mW lasers...
thanks for the clarification.
I've seen people talking about this way:
Two parallel lasers, one camera. When the lasers hit an object, the separation of the two spots in the camera view is less when the distance of the object is greater.
Basically I'm trying to expand on the idea of the backup sensors that you can find on cars today except at a longer range (around 30ft) so at 30 ft you would hear a beep and as the object moved closer the beeps would increase. I feel like you all should know what i'm talking about. So basically I am just trying to improve range on an already developed idea.
BigTop:
Basically I'm trying to expand on the idea of the backup sensors that you can find on cars today except at a longer range (around 30ft) so at 30 ft you would hear a beep and as the object moved closer the beeps would increase. I feel like you all should know what i'm talking about. So basically I am just trying to improve range on an already developed idea.
Like this one, only longer distance:
Up till now, we still don't know what you are measuring. If you have only one object you want to monitor its distance, you may attach a sonic ranger on it and signal another sonic ranger on the receiving end to simultaneously send out sonic waves. This way you can extend the detection range by at least 100% so maybe 12m on that sonic ranger I use, which is getting close to your 60ft range. You can even start one ranger later than the other and trick them to report a distance that you can covert to actual distance much greater than 60ft. This only works if you have one object to detect and it is constantly facing the same direction. But again, more details of your project need to be disclosed.
The basic idea is I want to hook one of these up to a bike and track the proximity of incoming cars while riding on the side of the road.
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Then what I suggested won't work. Probably lasers don't work either.
Lasers would work, other problem how to point it at a car, nobody ride on perfectly straight line, :~
The only alternative I can think is Radar - Wikipedia
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A highway patrol speedometer gun thing will work and you have to aim at the object. I don't think a small laser mounted on someone's butt is going to automatically point at the nearest car. Lasers are very hard to use at long distance. Sonic ranger has the property of larger angle and works nicely but only for shorter distance. You can, on the other hand use a supped up version to create more sound volume but ambient noise level may work against anything sound-wise.
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