Hi, I'm trying to find a way to sense the distance between two arduinos up to 180 feet away and no further with a resolution of an about inch. Is there any way to do this? Also, it would be important if it wasn't a laser so I don't have to arduino the arduino. Could it be like a radio wave moving out in a circle so that it doesn't matter which direction the other arduino is away? I've been doing research and can't find anything that meets this criterea. I know radio won't be accurate this close in proximity, so this there any way to get a faster clock microcontroller? Thanks!
There is currently no way to do what you want on an amateur's budget, other than a physical measurement (e.g. tape).
Care to explain what you mean by
so I don't have to arduino the arduino
?
I'm not sure whether it will work/what equipment you would need.
I wonder whether it's possible to use a combination of light and sound triggered at the same time.
A light beam will be detected almost instantly, sound travels much slower.
If the sound signal is detected 160 millisecond after detecting the light, distance should be ~180 feet.
...but remember, you're going to have to make a lot of noise to be heard 50+metres away.
Quite a bit of light, too.
Simpson_Jr:
I wonder whether it's possible to use a combination of light and sound triggered at the same time.
Or perhaps radio and sound. To be detectable at that sort of distance it's going to have to be pretty loud, though, and you'd need to choose a suitable frequency for the environment it was to be used in.
A Laser would work as well, but aiming may be a problem. Radio is indeed better/easier.
You would need to aim it, but maybe this article on Parabolic Microphones could minimize hearing loss ;).
but maybe this article on Parabolic Microphones could minimize hearing loss
Only $700.
Bargain
Keep in mind that the speed of sound is affected most by temperature then less by humidity and pressure.
Will the Arduinos have line of sight? That's key to a number of solutions.
If I set up 2 leds apart to make a width then how wide they appear to be changes with distance.
Just how you would determine that....
AWOL:
but maybe this article on Parabolic Microphones could minimize hearing loss
Only $700.
Bargain
Ouch, wrong one, even in a 4 for 1 sale, (why the ...k do I always forget to type DIY in my searches ?) 
Anyway, this one may be affordable, this one certainly is.
GoForSmoke:
Keep in mind that the speed of sound is affected most by temperature then less by humidity and pressure.
Now that you mention it, travelling in air, windspeed should... be... compensated as well.
It's indeed a lot of arduino-ing the arduino, measuring a piece of rope, will probably be simpler to get a 1 inch resolution. (measuring/ rolling it electronically would at least be easy using an arduino).
Interesting problem. You didn't give a very thorough description of the two arduinos - are the portable Arduinos? Outside w/ view of sky? On some kind of track where you can set up posts?
My first idea is to use a GPS module in each and transmit the location to each other. That'll get you within 10 feet if in open sky. From there, maybe use ultrasonic distance sensors to fine tune the distance off of posts that are set up every 10 feet? Basically, the GPS location tells you which post you're near, and the ultrasonic sensor tells you how many inches you're away from a known post?
I've been doing research and can't find anything that meets this criterea.
Natures warning sign, If nobody is already doing it, then it isn't going to be easy/cheap.
arusr:
Interesting problem. You didn't give a very thorough description of the two arduinos - are the portable Arduinos? Outside w/ view of sky? On some kind of track where you can set up posts?My first idea is to use a GPS module in each and transmit the location to each other. That'll get you within 10 feet if in open sky. From there, maybe use ultrasonic distance sensors to fine tune the distance off of posts that are set up every 10 feet? Basically, the GPS location tells you which post you're near, and the ultrasonic sensor tells you how many inches you're away from a known post?
GPS on each would give +/- some error each. Those tolerances may accumulate. 20 feet.