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corrected Symmes Creek switchbacks map

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corrected Symmes Creek switchbacks map

Postby SSSdave » Sat Feb 23, 2013 11:27 am

Image

Looking at the satellite image of the Symmes Creek Shepherd Pass Trail, I noticed the USGS topo trail did not at all match the satellite. Of course poorly added trail routing is rather common on topos because most of the time it requires someone to manually add them while actually walking a trail. In this case they could have drawn it from the satellite image.

http://mapper.acme.com/?ll=36.71054,-118.29764&z=15&t=T

Since the trail was mostly visible on the satellite image:

http://mapper.acme.com/?ll=36.72113,-118.29454&z=18&t=S

I decided to correct the bogus trail. So used mwsnap to copy that highly magnified image in several pastes into Photoshop, then traced over the trail in a separate layer. There were a few spots where the trail is not fully obvious like passing trees, but such are minor. After completing the trail, I measured the pixel height between where the trail leaves the creek at 6880 and reaches the top at 9080. Made a copy of the topographic map into another Photoshop window doubling its size, and measured the pixel height of the same points. That provided a scaling factor I then used to reduce the size to match the topo exactly. Then overlayed the trail layer into above the topo layer and added text. To view the map at the same scale as a USGS topo that is about 2.58 inches per mile, reduce the map scale by %50.

There are 52 total switchbacks versus the topo's 28. The total vertical for that section is 2200 feet. The bottom is 580 feet above the dirt road end trailhead at 6300 feet, so to reach the knob to cross into the Shepherd Creek canyon to the south requires 2780 feet of climbing that during summer midday is likely to be rather hot. Shepherd Pass is at 12040 but because the trail dips down to 8500 feet after the knob, the total vertical is 6400 feet.

This coming summer I have 4 backpacking trips planned including two 9-day trips with the last of those in August over this route and into the Upper Kern Basin. Since I carry a huge pack, I typically go uphill slowly taking many breaks, thus expect to climb over the pass early on the third morning. I noted a report verifying this switchback section is still in shade awhile during early morning in summer that one can see is the case by looking at how the north facing exposure is somewhat blocked by a rib just east to the morning sun. So my own strategy will be a dawn rise in order to reach the 8000 foot point up 1700 feet where the trail comes close to what I've been told is a reliable small stream. Then will take a long break before continuing on in minor chunks between breaks the rest of the way up to the knob whereupon will continue on to the next reliable water that is likely at least to the 8500 foot section. That will stage my effort to reach the Big Pothole area the next day which is just 1200 feet below the pass for day 3.



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Re: corrected Symmes Creek switchbacks map

Postby Baffman » Wed Feb 27, 2013 3:24 pm

Nice job on the switchback mapping.

How heavy is your pack? I climbed up to the pass in one hard day. It was a lot and my pack was about 34lbs. 3 days just seems like a long time. Water isn't a huge issue. I found the streams to be flowing well into the end of August.
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Re: corrected Symmes Creek switchbacks map

Postby SSSdave » Wed Feb 27, 2013 4:31 pm

Thanks, and since posting Bob Burd over on Summitpost has verified my changes closely match what he recorded on his GPS data logger.

http://www.davidsenesac.com/Backpacking ... cking.html

Yup most that do Shepherd or Taboose also tend to do those whole painful climbs in one day though I'd bet few bothered before starting to actually figure how many feet that is.

It is because I carry a bone crushing weight. The above link is rather dated from 2005 but will clue you in. Note my current body weight is up a wee bit to 140. Since then have reduced my average pack weights maybe 8 pounds by otherwise using lighter gear wherever possible. Last year a 9-day trip over the Silver Divide started at just 66 pounds. Since that trip will be going into Sequoia NP am also going to have to deal with adding the hated Garcia cannister.
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Re: corrected Symmes Creek switchbacks map

Postby giantbrookie » Wed Feb 27, 2013 7:34 pm

Nice. No doubt what you found is true of the rendition of most trails on topo maps. I guess on sections like the "opening grind" out of Symmes Creek I've never bothered to pay attention to the switchbacks on the map, figuring that "I'll know it's over when it's over". Of course the biggest heartbreak on that trail is having to give back 500' of that hard-earned elevation gain after that first saddle.
Since my fishing (etc.) website is still down, you can be distracted by geology stuff at: http://www.fresnostate.edu/csm/ees/facu ... ayshi.html
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