I have been using the VDO MC 1+(a baromater based) device for tracking my elevation gain during a ride. Last week when I checked a ride on routeslip.com, the elevation there was 4100' vs my VDO at 2900'. Another ride VDO recorded 1344 vs 1900 for routeslip. Seems routeslip.com is always higher. Can anyone comment or direct me to a thread that may enlighten me? I calibrate to my home elevation before every ride(509') and after today's ride plus 3 hrs the VDO reads 537 which I think is pretty close. thanks, carol