At a minimum you should start with free space loos calculation, you can find several simple calculators online. You will need to know the frequency of the radio, distance between the master and remote radio, and the gains of both antennas. You also need to account for transmission line, connector, & protector losses.
You need to look at the topology between the two antennas. Consider the ground elevation at the two antennas, the master antenna height, the elevation profile between antennas, obstructions in the path…etc., etc. etc. At a minimum, I would start with Google Earth and use their elevation profile feature. It isn’t perfect, but it will tell you a lot.
Also need to account for the trees, how high, what type, density, etc.
Need to know specifics of the radio you are using; frequency (band, licensed or unlicensed), power, receiver sensitivity, over air data rate, modulation scheme, noise floor in the area.
There is a lot that goes into a proper path calculation. I would recommend consulting a communications system engineer, or perhaps start with the equipment manufacturer to see if they can run a quick path study for you.
