I'm in 100% agreement with fowladdict on this. Some of you have probably seen my posts on 24hour regarding the accuracy of these gps maps compared to USGS Quads, actual BLM maps, and aerial photos. All of these gps maps use cadastral information the makers get from a variety of governmental sources. The cadastral shape files are based on GCDB information and therefor are only as accurate as the GCDB. Below is a map showing the accuracy of the GCDB information for Yellowstone County, MT. The orange areas are reliable to within 101-200 ft while the red areas are 201-440 ft. While a lot of the county is pretty darned accurate, there are also many areas where your gps mapping software is going to show boundaries that are off by 100 yards. I have the huntinggpsmaps.com software on a work gps and while it is "close enough" most of the time, I've had more than a few experiences where driving down a county road that I know is the section line, and there's public land that runs along the road, but the map shows me driving 50-60 yards away from the road and public land, to not be uber-confident in its accuracy. I will say, though, that the information these maps rely on is getting better and is quite a bit more accurate than it was five years ago. I usually go on a much longer diatribe about how superior the DeLorme units are as a hunting platform but will spare you all the agony!
In a nutshell, a fenceline that doesn't agree with your gps may in fact not be on-line and the gps may be correct. But, your gps map could just as easily be off by 100 yards so take what it's showing you with a grain of salt.
In a nutshell, a fenceline that doesn't agree with your gps may in fact not be on-line and the gps may be correct. But, your gps map could just as easily be off by 100 yards so take what it's showing you with a grain of salt.