by Snowhiker » Mon Jul 10, 2006 8:03 pm
I remember the 10,804' vs 10,834' thread as I'm the one that started it! When I first saw the new San Jacinto summit sign, I thought that someone has simply screwed up, as I've never seen the 10,834' number used anywhere. That was the reason I started the thread. If the 10,834' reading was from a more recent or more accurate survey I haven't seen it posted or mentioned anywhere else.
From all the web sites and messages I've read regarding GPS receivers (GPSr) it seems that consumer grade GPS units (under $2000-5000) are NOT going to give you an accurate elevation reading. For consumer grade GPSr horizontal accuracy is between 20-30 feet, while VERTICAL accuracy is between 100-200 feet, or more, AT BEST. This is assuming perfect reception, excellent satellite geometry and accurate WAAS correction data. The GPSr may give you an accuracy number (mine gives a number between 6-14' on good days) but this number is not to be taken as fact.
GPSr can obtain elevation using two different methods. The first being GPS elevation. GPS elevation requires a lock on at least 4 satellites and its accuracy is determined by geometry, reception and WAAS corrections among other things. The second method is using a barometric pressure sensor built into the GPSr. You need to calibrate the elevation from a known point, and get to the summit before weather conditions change to obtain the most accurate reading.
The last few times I've been to the Summit I didn't take my GPSr, but the next time I go up I plan on taking it.
Please take a GPS reading from the Summit as I'd be very interested it what the results indicate.