On Sep 14, 2013, at 2:13 AM, Darren Addy <pixelsmi...@gmail.com> wrote:
> Elevation of location. (ASIDE: This seems to be where "all GPS units > exhibit a weakness" but I'm not sure why that is. According to this > PDF, > http://www.nasa.gov/centers/johnson/pdf/584738main_Wings-ch5c-pgs360-369.pdf > the space shuttle created topographical data sets that can give the > elevation for virtually any location. Perhaps it is just not built > into the GPS system yet, or there is no method for the GPS to "look it > up" and enter it into the calculations.) FWIW I think Garmin Connect uses that database. There's an "elevation correction" option that you can activate. It's not much good when you're out and about though as this is only done after you've come back and uploaded your route :) What Matthew said about the difference in accuracy is the same as what I'd heard so I've deleted my version of the same explanation. My Garmin watch uses a barometric altimeter which auto-calibrates whenever I'm near a known location (ie somewhere I've programmed into the watch with its elevation). If the altimeter goes wonky it will switch to GPS elevation, but the manual doesn't say the exact conditions under which this happens. Being barometric it is of course susceptible to changes in weather conditions but once it's calibrated it's pretty good: good enough to give me a fairly accurate gradient reading on the hills. Cheers, Dave -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
