Remember that post about the peak being 10804 or 10834?

General Palm Springs area.

Remember that post about the peak being 10804 or 10834?

Postby zippetydude » Fri Jul 07, 2006 7:53 pm

Okay, the issue was left unresolved. I lost my gps, so I couldn't go find out. Well, I just ordered a Garmin 305, so I'll be back with a posting on the most current reading in a week or two. I might have a chance to do it this weekend, but the San G wilderness is calling to me...

In any case, does anyone else have a recent reading? I want to compare what I get to what others are getting to calibrate mine. Any numbers out there?

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Postby phydeux » Fri Jul 07, 2006 8:20 pm

My USGS 15 min map says 10.804 ft
My USGS 7.5 min map says 10,804 ft
My State Parks map says 10,804 ft
John Robinson's San Bernardino Mtns book says 10,804 ft
I've got some old photos that say 10,804 ft on the summit sign

10,804 ft sounds pretty convincing to me!
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Postby robpollard » Fri Jul 07, 2006 9:07 pm

I can see the temptation to use a GPS, but before you believe the results, check the documentation to see if it says what the accuracy (for elevation) is. Some GPS units (like the Garmin 305) use atmospheric pressure to determine elevation, so the current conditions might impact the reading (esp. down the level of +/- 15 feet). Just my opinion.
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Postby phydeux » Sat Jul 08, 2006 8:22 am

A follow-up:

Cant' say whether its 10.834 ft or 10,804 ft; not really too concerned about the details. Whatever it is is what it is, and what it is is a great view from the top! :D
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Postby zippetydude » Sat Jul 08, 2006 12:50 pm

Two things:

Phydeux, you make a very good case. Sounds like the 10834 is just a typo that slipped in since there are apparently lots of other sources saying otherwise.

Rob, sounds like you know more about it than I do. I thought the GPS used triangulation to establish altitude, just like it does to establish location on a two dimensional plane. Does it use atmospheric pressure as well, and average the two estimations, or does it simply go from an atmospheric reading? I remember my old Garmin Etrex Legend taking a readings on top of San G. The marker says, I believe, 11502. On two different trips the gps came back with 11504, so however it was doing it, it was fairly accurate and pretty consistent. Have you found that the plus or minus is just being cautious, or that they really do vary in their estimations of altitude?

In any case, thanks to both you guys. I learned something here.

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Postby robpollard » Sat Jul 08, 2006 3:11 pm

zippetydude,
I don't really know that much, only what I picked up from a friend. He has the Garmin 305 for his bike, and I know from him that the unit uses barometric pressure to measure altitude. Sometimes when we get back from a longish ride (5 hrs + say), his house will be as much as +/- 20 feet from where it was when he calibrated it in the morning. With this, plus the fact that he has to calibrate it to start with, I assumed there is a normal error.
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GPS accuracy

Postby 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.
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Postby Guest » Mon Jul 10, 2006 11:06 pm

If I get my 305 before the weekend, I'll take it up and get a reading. I'm hoping to get it, then do the C2C route so that I can take it home and download the entire track. TopoUsa can run a 3d image of the map, and I can follow the track and watch my progress along the way. Kinda fun.

Another thought on the 10834 number - suppose there's anyway to trace it backwards and find out where it originated? Some clever sleuth could probably figure out a way to do that. I'm not that clever, but there may be someone out there...

By the way, it says you're from Surprise, AZ. You get to visit the wilderness often? Any cool peaks out your way? I went up Thumb Butte by Prescott once - easy hike, I did it pushing a stroller - but a cool trail nonetheless.

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Postby zippetydude » Mon Jul 10, 2006 11:08 pm

Oops. Forgot to sign in. That was me above.

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Move to AZ

Postby Snowhiker » Tue Jul 11, 2006 11:49 am

Moved to Surprise (NW of Phoenix)AZ in December of 2005, but spent the rest of my life in Orange County California. I've been to Jacinto and Gorgonio many times. Never did C2C.

Not much hiking in the greater Phoenix area now as it's 110+ during the day, and lows of 80/90s. You can do a different nice day hike every weekend for at least a year in the greater Phoenix metropolitan area. No Jacinto/Gorgonio class stuff as far as elevation gain but a wide selection.

I have done quite a few car day trips in AZ, and there is an amazing amount of stuff to do. Grand Canyon, Sedona, Prescott, Flagstaff, Mt. Humphreys (12,633'), Tucson, Mt Lemmon (9,500'ish'), etc. It's just too hot right now.

I do miss my old local mountains and Cleveland National Forest.
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