Bob W wrote: > I know nothing about this subject, but I won't let that stop me > pontificating. If it's barometric then it measures altitude using air > pressure, which changes with the weather, as well as with the > altitude. Mountains tend to make their own weather, so I would have > thought a barometric altimeter would have a few problems. > > http://wiki.motionbased.com/mb/GPS_Barometric_Altimeter
Indeed, that is the case. You have to calibrate a barometric altimeter at the beginning of the day's journey (at a point for which you know the exact elevation). If there are significant weather changes, you may have to calibrate several times in a day. Barometric altitude is offered as an option, however inconvenient, mainly because GPS positioning is far less accurate in the vertical direction than horizontal. Oh, and those signs that tell you the elevation at scenic viewpoints are often questionable in accuracy, too. In short, it's a mess. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
