I backpack, hike, kayak, canoe, and cross-country ski. Oh ... and I cycle. My budget can't afford separate GPS units for cycling and all those other things so I bought a Garmin Oregon 450t handheld unit and the bracket to mount it to my handlebar (it works with a cadence sensor and HRM, too!).

The Garmin 450t has a "Trip Computer" screen that lets me see a variety of things: time of day, distance, moving average, average speed, maximum speed, etc. I did my first century the other day and was surprised at the inconsistency between the data displayed on the Trip Computer screen and the uploaded data (to Ride With GPS).

The screen said 101.5 miles but the uploaded track says 100.9 miles. That I understand - the trip computer is giving me realtime GPS positioning data and measuring my distance accordingly whereas the track data is calculating point-to-point distances (the unit is set to drop a track point or breadcrumb every 0.02 mile or about every 105 feet). It will shortchange me a little distance on curvy roads or when turning a sharp corner. Even with that, the uploaded track was within 0.6% of the Trip Computer which - to me - is totally acceptable.

What sort of astounded me was the difference in moving time. The trip computer said 6:47 but the uploaded track data said 6:32 ... a difference of 15 minutes or about 3.6%. A friend I did the ride with used a Garmin Edge and her stats came up at 100.8 miles and 6:34 moving time - both of which are pretty darned close to the uploaded data from my unit. The difference in moving time - from 6:47 down to 6:32 - bumped up my average speed from 14.9 to 15.4 ... I like that but I'd like to have relatively accurate data.

My question: Before I call the Garmin support number, have any of you experienced this "time warp" and can you help explain it to me?