I have never had any experience with a GPS unit at all. So I am quite green at this. I notice most on line maps dating back to 100 years or more are pretty much spot on when they show a structure such as a old school, church etc. These on line maps will show the coordinates. What would be a recommendation for a good handheld unit. I would like to put those coordinates into the unit and then be able to walk to that location even though there is no visable sign remaining of it.