Thanks for helping. I'm looking for a system that will help me find exact distance between a transmitter and receiver at a frequency of milli seconds, in distance accuracy of milli meters.
I want to avoid environmental factors, reflections or line of sight issues. My initial idea is to have a transmitter pulsating at 30 msec. Use the time taken between signals received to calculate the exact distance. Initially I am looking for a range of 20 m. But in future I would like to explore the idea of upto 1000m.
I think GPS wouldn't work, I am open to any modulation techniques. Are there any pre existing modules?