I know a fair amount with electronics, so i was PRETTY frustrated when i looked around online for a method of rangfinding that i could build into a small device. I have been wanting to have a project for awhile, so i am not just going to buy one. Anyway the inspiration comes from me and my dog, you see, hes a Jack Russel, and very eager, he loves to chase rabbits but i can never find him after he has run off into the forest, by that time he is too far away to hear me.I want him to chase rabbits because he loves it, but i can't use a lead because it gets caught on everything(Trees, plants, thorns and general vegetation).So i had an idea, if i could just have a device that would tell me how far away he is, then i could just use that to work my way towords him.The process seemes quite simple to me, give him a transmitting collar, and have a device that recieved that signal, and could use the basic distance = speed x time sum to work out how far away he is, then display it. Apparently, either nobody has ever tried this, or i just ain't searching for the right thing.I know radio waves seem to be optimal, seeing as he won't be more than 1KM away from me, but again, i don't really know where to look to find the parts, or how to build the thing in the first place. So please, if anyone could help me out, please do.My physics teacher is a real **** and refuses to help me.So you guys are all i have to ask. Thanks. /James PS: My dog would be REALLY happy too, he hates being on a lead all the time, and if i could get this done, i will post pictures of him, apparently hes really cute.