Caltopo MapBuilder Topo for mileage

[SSSdave]

We often read requests asking how far on trails it is from X to Y. A person can easily do this themselves via the caltopo dot com site. Standard USGS topographic maps do not have that information and older information actually signed on trails or in guide books may be somewhat incorrect either due to trail routing changes or the various older crude manual methods used. Given GPS tracking, it is now easy to total up mileage on such routes with better accuracy.

Caltopo has been putting such point to point mileage on their MapBuilder Topo display with the Base Layer mode one can select at window upper right. As someone that has manually estimated mileage on topos for decades, I find their numbers excellent. I may backpack over McGee Pass by early August and have adjusted my old measurements slightly to fit their numbers. If one wants to know mileage on off trail sections, will suggest on a paper printed out map or USGS topo, find the map scale, pencil lines for a route, and on a folded piece of paper, pencil on the edge, 1/4 mile increment marks to make rough measurements against trail lines with. If one is wondering how well they are doing so simply try measuring a reasonably straight measured section on MapBuilder Topo for comparison.

https://caltopo.com/map.html#ll=37.4800 ... z=14&b=mbt

[Wandering Daisy]

Coincidental that I was about to put in a post regarding mileage. I took my Garmin watch on my last two trips, and it automatically counts "steps" to estimate miles. Since the watch has "learned" my stride from dog walks on sidewalks, it obviously overestimated my mileage when backpacking. When I turned on the actual GPS function, the mileage was quite accurate, on the road walk from Agnew Meadow to the gate (3 miles). But this wears down the battery quickly, so I use it sparingly. When I wear the watch all day, it also picks up ALL my steps- setting up the the tent, walking around camp, etc.- which is actually considerably more than one would guess. These camp "steps" are usually smaller steps, so again the watch will over-estimate.

I do not use an actual GPS, but my understanding is that you set the timing of each data point. The longer time between data points the less accurately it reflects your actual path.

Map mileage (and less so, GPS miles) is not the same as the actual miles you walk. Not only is the map a crude representation of the trail, we continuously take small detours to avoid rocks, puddles, etc. I use the drawing function in the old "TOPO" program to plan trips. It is just an automated form of the old map "wheel" where you run a small wheel along a trail shown on a map. In general my actual walking is from 5-20% more than the map miles. The upper end is reflective of off-trail travel where you do many more small detours than on a trail. Trails with a lot of switchbacks are difficult to "measure" on a map. Not all switchbacks are shown on the map and what is shown may just be a crude representation.

As for old mileage on signs, some actually was determined by running a larger wheel along a trail. Of course, if the trail changes, the old mileage is off. Some mileage on signs is estimated from maps. Some "measured" from air photos. All these methods have some degree of distortion. And then sign mileage is often "rounded".

I am quite leery of miles taken from crowd sourced GPS tracks. Whatever the source, be sure to look for documentation of details on how the miles were derived.

SSSdave- how are Caltopo MapBuilder miles calculated? Is it the same as the draw function on the old TOPO? Or is it based on GPS tracks? Or something else?

[SSSdave]

Thanks for your input WD. Suspect the caltopo numbers are from multiple GPS users or someone they trust with a higher quality GPS unit. Someone might ask directly. As noted, I have found the caltopo numbers closely track my own manual methods that have always been close to Wilderness Press guidebook numbers. In any case all we enthusiasts need is mileage roughly to tenths of a mile accuracy.

Decades ago I ran into Tom Harrison with one of the bicycle wheel tools along a Mono Creek trail. Many topo map trail lines are of course inaccurate which is why redrawing them from GPS tracks has been a significant improvement. On this page I show a GPS revised trail of the Symmes/Shepherd Saddle trail Bob Burd made, an example of how bad that often is on maps.

https://www.davidsenesac.com/2019_Trip_ ... 019-7.html

[Enigmagic]

SSSdave- how are Caltopo MapBuilder miles calculated? Is it the same as the draw function on the old TOPO? Or is it based on GPS tracks? Or something else?

Thanks for your input WD. Suspect the caltopo numbers are from multiple GPS users or someone they trust with a higher quality GPS unit.

Caltopo's MapBuilder trails and roads are imported from OpenStreetMap. Caltopo runs an import a few times a year. Most of the OSM trails started off as the (rarely accurate) USGS or USFS trails, over time many of these have been updated by hand. Some with survey quality GPS units, but most are derived from a mix of sources including satellite, lower quality gps tracks (like a Garmin watch or phone) and Strava heatmaps. The quality should generally be very good aside from problem areas with dense tree cover on steep slopes. If you find errors in the OSM trails you can update it yourself or let me know and I'll do what I can to fix it.

[SSSdave]

Thanks enigmagic...a valuable resource on the board. Now for the question of the day...

Would a woodchuck chuck wood if a woodchuck could chuck wood?

Since I might bring my fishing bro back up into these areas later this summer after squeets are well gone, made this map to help ideas. From caltopo Map Builder Topo. So much for horse trails.

The black numbers are mileage the map shows if zoomed in one more level. The gold numbers are my estimates where no mileage is shown. The yellow route from the Hoffman Mtn road gate is where 3 of us went in 2001 and then giantbrookie repeated. The dots from Scepter Lake is how we headed to Blackcap Basin. Magenta dots are other obvious crosscountry routes if one looks at Google Earth, GE. Just going to Marsh Lake shaves off about 3 miles and vertical. Even Crown Lake is just 7 miles via a totally crosscrountry route. Another option doing that would visit Duck Lake the first day.

The Hoffman Mtn road is poor, has gates and may have damage if not recently maintained. An alternative is to use the lower Little Rancheria Creek trailhead that shows no trail however GE looks like one could climb up to the regular longer horse trail that adds 300 feet. Even if one manages to reach the Hoffman Mtn gate at 8360+ this is not crosscountry for amateurs. Tall trees in mosquitoey realms make this for constant compass plus topo use and yes there are willow thickets and chinquapin.

(mouse select to enlarge and remove blurryness)

HoffmanMtn1.jpg