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correction to Symmes Creek switchbacks topo

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correction to Symmes Creek switchbacks topo

Postby David Senesac » Sat Feb 23, 2013 7:02 pm

Image

http://www.davidsenesac.com/_a-z_evad/B ... mescr2.jpg

Looking at ther 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 it 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 linked 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: correction to Symmes Creek switchbacks topo

Postby KathyW » Sun Feb 24, 2013 2:06 am

As I recall there is an old trail and a new trail - the old trail has less switchbacks; so the topo might not be that far off if it is showing the old trail.
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Re: correction to Symmes Creek switchbacks topo

Postby David Senesac » Sun Feb 24, 2013 2:31 am

KathyW wrote:As I recall there is an old trail and a new trail - the old trail has less switchbacks; so the topo might not be that far off if it is showing the old trail.


Thanks Kathy, could be though I would expect such would be obvious on the satellite. Maybe someone climbing up that trail can print out the jpg to compare and amuse us. You might look at the satellite link. Most obvious section that is way off is near the top where the visual switchbacks are well east on an open brushy slope from where the topo trail shows. Note on the ACME link when one switches between the Topo and Satellite tabs, registration of the center + cursor is the same spot so one can zoom in to the exact same location between the two modes and thus evaluate where the visual is showing.
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Re: correction to Symmes Creek switchbacks topo

Postby KathyW » Mon Feb 25, 2013 2:01 am

It's one of those trails that has been improved for stock, which often makes them more difficult for those traveling on foot. So many of the trails are that way anymore - I try to take the old sections of the trails if I can find them because they don't have as many switchbacks or big stair steps. I don't think the old trail is real obvious on that route - probably not at all from a satellite image.
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Re: correction to Symmes Creek switchbacks topo

Postby Bob Burd » Mon Feb 25, 2013 4:00 am

In Secor's first edition, he gives the trail length as 12 miles (to the Tyndall Ranger Station, not Shepherds Pass). In the second edition it is 13 miles and in the latest it is 14 miles. I think the second edition simply underestimated how much mileage was added to the trail when it was reworked. I've been up and down that trail almost a dozen times and I've never found much evidence of the old trail. I've heard that others have done better in this respect and used portions of it, but it can't be much of a time-saver unless you're bombing down the slope in trail runners with little more than a water bladder on your back.

For what it's worth, this map shows a GPS track overlayed on the topo map. It pretty much matches what you have drawn by hand from the satellite views.

Oh, and I remember counting the switchbacks once. I got 66, but that could have been an exhaustion-induced exaggeration.
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Re: correction to Symmes Creek switchbacks topo

Postby Teresa Gergen » Mon Feb 25, 2013 3:20 pm

BTW, it's much easier to do mapwork like this at caltopo.com -- call up the area, flip to the satellite view, draw a line following the trail, then flip back to the topo view. When you're mapping a cross-country route, you can do this to draw a line that avoids the most boulders, brush, etc, or to find the gully that Secor is most likely referring to when it's not obvious from the topo map. Routes can be downloaded from caltopo as GPX files and then uploaded to TOPO! or a GPS. They can also be exported to Google Earth so you can see your route in 3D in advance, and make sure you've drawn the right/best-looking route before using it in the field.
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Re: correction to Symmes Creek switchbacks topo

Postby David Senesac » Mon Feb 25, 2013 4:52 pm

Bob Burd wrote:In Secor's first edition, he gives the trail length as 12 miles (to the Tyndall Ranger Station, not Shepherds Pass). In the second edition it is 13 miles and in the latest it is 14 miles. I think the second edition simply underestimated how much mileage was added to the trail when it was reworked. I've been up and down that trail almost a dozen times and I've never found much evidence of the old trail. I've heard that others have done better in this respect and used portions of it, but it can't be much of a time-saver unless you're bombing down the slope in trail runners with little more than a water bladder on your back.

For what it's worth, this map shows a GPS track overlayed on the topo map. It pretty much matches what you have drawn by hand from the satellite views.

Oh, and I remember counting the switchbacks once. I got 66, but that could have been an exhaustion-induced exaggeration.


Thanks Bob, your input verifies that. GPS tracking is a very useful way to correct such. There were some mini-switchbacks I might have counted adding to the 52 but given the satellite granularity such ought really only be done actually walking the trail. Thus 66 is a likely improvement on reality. Someone ought to do the same going up the switchbacks above Groundhog Meadow above Mineral King which is even worse. With that done, I'll work on it a bit more and roughly measure the new trail length. Note I had already measured the topo trail as 12.1 miles to Shepherd Pass so that is certain to grow. I roughly measure topo sections in 1/4 mile segments by placing an edge of paper marked so extrapolating for gradient and likely windiness that generally closely matches on all manner of trails work done decades ago Wilderness Press in Sierra North/South.
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Re: correction to Symmes Creek switchbacks topo

Postby Tom Kenney » Tue Feb 26, 2013 12:57 am

You can still see parts of the old switchbacks. Occasionally you'll see a steeper trail remnant cross the current trail, and will notice stone walls. The old trail was obviously unpleasantly steep, but the new one, IMHO, is too shallow.
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