Why Not Use GIS? Because… Google
This video briefly goes into why not to use the county GIS mapping system over other applications like Google Earth. Read on for more details!
As you saw in the video, there are a number of reasons not to use the GIS system. First and foremost should be the GIS system's own disclaimer that pretty much states it all. See my county's disclaimer below. I have bolded some areas of importance.
Application Use and Mapping Disclaimer
This map is neither a legally recorded map nor a survey and is not intended to be used as such. The information on Mecosta County websites, are distributed and transmitted ‘as is’ without warranties of any kind, either expressed or implied, including without limitations, warranties of title or implied warranties of merchantability or fitness for a particular purpose. Mecosta County does not guarantee the accuracy, timeliness, or completeness of the information on this website.
The Geographic Information System (GIS) made available through this website is developed and maintained by Mecosta County. Use of materials and information constitutes acceptance of all disclaimers associated with these websites. GIS data is not the official record of the County. This data is made available for information purposes only!
Aside from the above, the property boundary overlays on the imagery make it impossible to do any real figuring (at least for my county). The houses, roads, lakes, and easements are overlapping the imagery in a way that do not allow for accuracy.