I've had my EZGuide+ give me a bad area calculation twice that I know of this year.  Did one field with my Garmin and EZG going at the same time.  Two different areas, so I assumed the in-cab Garmin was wrong (4.8a vs 5.3a with the Garmin).  Did it again with the EZG and got the same area as the Garmin gave me.  Did it again with the tractor and got the same as the Garmin again.  Got out of the tractor, walked the field twice.  Got 5.6 once (with Garmin on battery saver) and 5.3 the second time on normal with WAAS.  I thought it was a fluke caused by doing an area after restarting the tractor (which powered up the EZG) and doing the area too quickly.  

 I tried another field the other day and got 6.8a and shook my head because the field seemed between 3 and 4 acres but definitely under 4a.  Walked it with the Garmin and got 3.2 acres. 

 Shouldn't a sub-metre GPS give just about perfect area calculations repeatably?  Before anybody asks, I double-checked that my equipment width was set right and did the area calculation based on the right implement edge while travelling counterclockwise.  Anybody else get wacky results like these or do you always assume that the EZG is accurate?