getting planter calibrated and running a new to us 2010 Case 1200 planter this year w/ 600 monitor. can hook it into our Trimble RTK and figured that would be easiest. however...when looking lately at speed differences displayed via the Trimble RTK and an AgExpress sensor we had for a Raven controller...I'm noticing a fairly consistent variablility in the speeds displayed. Off the cuff "average" speed difference at any one time of around a half mph at a target speed of 5mph. Raining today so have not just measured a distance and done the manual calculation/calibration....so wanted to ask here first. Have yall seen this kind of variability before, and which one would you suspect right off as having the issue?