I don't know where you live, but in my layman understanding of the law the police has nothing on you if you just walk on land that is not immediately recognizable as belonging to someone (e.g. not fenced), and you don't damage anything that would obviously belong to someone (like trampling a field of grain).
Maybe the owner could come and rightly tell you to fuck off their land, maybe they could call the police and they could then say the same, but they can't fine you or anything. It's not a crime.