You should first decide what is a typical distance you need to measure. Then you should consider the situation: if you need to measure for instance a distance from a fixed location to another location over say 1 km, then you can use a pulsed radar if you can make sure the RF pulse can be reflected from the far location and ground clutter separated from this reflection. (you can put a reflector there).
If you can locate RF transceivers at both ends, you can send a RF signal from one point, get it received at the other, and returned back. Such devices were named Tellurometers many years ago but now laser range finders are used instead.
There are many options depending on your situation. Give us details, then we can offer a solution. General talk makes not much sense.