I wish we had GIS here, the town is working on it. We are a bit behind the technology curve here. Our counties are less involved in that sort of stuff than the individual towns.
If GIS is available, or your own land survey in digital, using the "track" function on a GPS unit with upload capability is supposed to work pretty good. Just walk around the area you want to map with tracking turned on, upload that and add it to the digital map. That's my understanding, maybe someday I will be able to do that. I would have to upgrade from my ancient Garmin GPS III unit.
I am tempted to ask the survey company that did ours if they can provide my survey in digital form. I would have to get the software for the PC, etc.