Sup /out/
Recently my father in law acquired some land and allows me to hunt on it.
I'm planning on going for ruffled grouse and hare.
My problem is that his land plot is a rectangle and not completely parallel to an imaginary South-North line. (similar to pic-related).
His neighbours are assholes and don't want me hunting on their land. I've never been there before but I have the coordinates on google maps.

My question is, what is the best way to navigate on his land so that I don't venture out of it too much?
I'm thinking of using some Android app with Localisation and pre-printed coordinates of the extremities of the land plot. I would check it every now and then and make sure I'm not trespassing too much.

Do you know of any app that allows you to set a rectangular area of land on a map and that can tell your location based on it?