I've not actually tried this but GPS provides 3D based on a reference ellipsoid earth shape rather than a geoid, so the GPS altitudes are not that accurate.
The Garmin GPS such as the 60C, which are not fitted with baroalt, deliberately omit the display of the
GPS altitude - otherwise they would have difficulty selling the baroalt devices.
If you upload your track logs, the device will include the GPS alt for later analysis - if you can wait that long.
Taken from newgroup discussion:
"However, after using this information to determine 3D velocity, the receiver then calculates horizontal and vertical velocity (the
components of velocity parallel to and perpendicular to the local horizontal). And it's the horizontal component of velocity that seems
to be reported as "
speed" in the user interface. Vertical velocity may be available in the NMEA data stream."
dave
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| I have a Garmin eMap which IIRC is a very similar device and I have the cycle mounting on the motorbike 
Actually altitude makes little difference IIRC - except for speed calculations. Jump off a cliff with your GPS and you'll see 0kph | |
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