USGS topographic map GPS trail corrections

If you've been searching for the best source of information and stimulating discussion related to Spring/Summer/Fall backpacking, hiking and camping in the Sierra Nevada...look no further!
User avatar
druid
Topix Acquainted
Posts: 51
Joined: Mon Aug 08, 2011 12:50 pm
Experience: N/A

Re: USGS topographic map GPS trail corrections

Post by druid » Sat Apr 03, 2021 11:59 pm

SSSdave wrote:
Mon Mar 08, 2021 1:48 pm
Experienced Sierra Nevada backpackers have over decades been aware of how ridiculously inaccurate some USGS topographic map dashed black line hiking trail elements have been. I won't go into a list of reasons that is so. Since GPS tracking devices arose, more accurate trail lines have been possible, especially when used with satellite imagery. My brief input herein is for those planning trips, a way to reduce that issue is to use caltopo dot com in the below modes that will show both the USGS dashed lines and GPS track paths. This can be especially confusing at trail junctions and places a trail crosses streams. There are also websites with GPS tracking captures from individuals one could also use.

In the upper right caltopo Map Layers pane, select Scanned Topos. In the Map Overlays pane select MapBuilder Overlay. Below shows how incorrect that looks from Mineral King to Sawtooth Pass:
https://caltopo.com/map.html#ll=36.451 ... &b=t&a=mba


We just did the climb from Mineral King to Sawtooth Pass last August and I can report that we were much happier following (roughly) the USGS dashed lines from Monarch Lakes to Sawtooth than we would have been trying to follow the MapBuilder route. We could see a fair number of parties doing the "one step forward, two steps back" direct sandy climb and none of them looked particularly happy. Even some of the people coming down looked fairly hesitant, although to be fair others were whooping it up as they boot skied down. I can't comment on the descent as we returned over Glacier Pass and so we ended up coming down much the same way we went up. I'm not sure how a MapBuilder route is constructed but if they are based on Garmin heatmaps or some such then they might well be the most popular route but they aren't necessarily the best one.








User avatar
Enigmagic
Topix Acquainted
Posts: 51
Joined: Tue Aug 15, 2017 7:40 am
Experience: Level 3 Backpacker

Re: USGS topographic map GPS trail corrections

Post by Enigmagic » Wed Apr 07, 2021 9:23 am

druid wrote:
Sat Apr 03, 2021 11:59 pm
I'm not sure how a MapBuilder route is constructed but if they are based on Garmin heatmaps or some such then they might well be the most popular route but they aren't necessarily the best one.
MapBuilder trails are trails as exist in OpenStreetMap. you can edit them if you're so inclined, every bit of help is appreciated. they're usually created from a mix of GPS recordings, satellite imagery, USGS topos, and yes, the Strava heatmap. Caltopo imports the OSM database a few times a year... updates made in OSM take 3-6 months to show up in Caltopo.

if you know where the lower part of the trail on the USGS map is you can add it in, it's currently missing: https://www.openstreetmap.org/#map=17/3 ... -118.56651

User avatar
SSSdave
Topix Addict
Posts: 3092
Joined: Thu Nov 17, 2005 11:18 pm
Experience: N/A
Location: Silicon Valley
Contact:

Re: USGS topographic map GPS trail corrections

Post by SSSdave » Wed Apr 07, 2021 12:11 pm

Sawtooth Pass will not have a standard trail route but rather many use paths. The nature of steeps and sands. Some peakbaggers with tiny packs will on descent always plunge step down the loose sand areas that backpackers with heavier packs should not follow. Also won't ever have any horses haha. Once down below Glacier Pass junction, best to avoid the sandy areas below the rib and instead climb or descend the firm bedrock area. Google Earth 2014 views. I posted some of this after two of of did this a few years ago as I carefully figured out the best route IMO.
Sawtooth1.jpg
Sawtooth2.jpg
Sawtooth3.jpg
Sawtooth4.jpg
Sawtooth5.jpg
Sawtooth6.jpg
You must be registered and logged in to view the files/photos attached to this post.

Post Reply

Who is online

Users browsing this forum: AaronRDavis, Bing [Bot], F14Rainman, hsv and 10 guests