Guest ba.roberts Posted February 25, 2001 Share Posted February 25, 2001 What sort of elevation accuracy would you expect to get with a handheld GPS receiver such as the Magellan GPS315? A friend and I (he has a Garmin) seem to get some strange results, but we are trying them in central London. [This message has been edited by ba.roberts (edited 02-26-2001).] [This message has been edited by ba.roberts (edited 02-26-2001).] Quote Link to comment
Guest peter Posted February 26, 2001 Share Posted February 26, 2001 Because of the basic geometry of the satellites you can see (i.e. none are below you), the vertical accuracy is worse than horizontal accuracy by about a factor of 1.5 - 2. So under ideal conditions, the altitude should be within about 15 - 20 m most of the time. But conditions are rarely ideal, and in a city the only satellites you can see may be almost directly overhead which will degrade the accuracy. And if you can only see 3 satellites, the unit won't be able to determine the altitude at all. BTW, older Garmin's (incl. the III+) seem to have a slight systematic error in the altitude calculation of about 10 m. Quote Link to comment
Guest ba.roberts Posted February 27, 2001 Share Posted February 27, 2001 Thanks Peter that's reassuring. We began to think we were going mad when it couldn't tell the difference between Ground Level and the the 8th floor. Quote Link to comment
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