Death Valley
Benchmarks, survey markers, and maps - Printable Version

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Benchmarks, survey markers, and maps - edward - 2024-03-16

I have a few question for those who have a better understanding of benchmarks, survey markers, and maps. Last weekend I found the marker below approximately HERE on the way to Lost Lake:

[Image: 6.png]

In the snippet below, the location for that marker appears to match the lower left corner of the central red box in the snippet below (full map here; source):

[Image: 7.png]

I am wondering what the data on the marker (i.e. "1/4", "S36") means. I believe the arrow on the marker was pointing due east, but I didn't verify it against my compass at the time. On the map, are the red boxes considered the equivalent of townships, and why are the red boundary lines not always connected? Thanks!

RE: Benchmarks, survey markers, and maps - edward - 2024-03-16

I am not sure what map they are using, but I snipped the following off of Peakbagger:

[Image: 8.png]

I believe I found the marker close to the number 36. I am guessing that identifies a section of a grid.

Edit: Per wyethia's comment below stating that the "1/4" on the marker indicates it would typically be found "halfway along the boundary of the section", I checked the GPS coordinates I have for the marker with an overlay of this map and satellite imagery in CalTopo. Sure enough, the marker is actually at the midpoint of the northern boundary of T 18 1/2 N... just a few feet off on the east side of old 4WD trail that is depicted.

RE: Benchmarks, survey markers, and maps - DAW89446 - 2024-03-16

The marker in your first photo is a cadastral marker. Cadastral survey markers are used to mark boundaries. Examples include section corners, quarter corners, witness corners, etc., or may exist just to note a boundary of a park, BLM land, etc. They typically do not include any information about elevation and are not related to bench marks, although they are typically marked by the same type of disc.

On your last map, which appears to be a standard 7.5 minute quad, there is a benchmark noted along with its elevation. Benchmarks can be divided into two general groups: the "vertical control points" are points that mark a very precise elevation above the standard datum plane (usually referred to as elevation above sea level) and the "horizontal control points" are points with precisely established latitude and longitude.

Other than that, I have never taught myself on townships. One member of this forum, Ski3pins, is well versed in maps and orienting himself on it without a GPS, as he is retired from a career in mountain S&R and teaching teams. You might PM him. He and his wife are currently in Death Valley.

RE: Benchmarks, survey markers, and maps - MojaveGeek - 2024-03-16

I think you refer to the red markings of the PLSS, Public Land Survey System. It is/was a set of northing and easting coordinates based off one of several baselines, mostly San Bernadino in the Death Valley area, but maybe the Owlsheads are far enough south to be in a different one?

Anyway, it is rather arcane, but if you google around for PLSS for a while you can learn to decode it. And there is some USGS ? site which can overlay the PLSS coordinate system. The red lines are "sections" which are divided into quarters, etc.

RE: Benchmarks, survey markers, and maps - edward - 2024-03-17

@DAW89946, @MojaveGeek: Thank you for the replies!

Thanks for pointing me in the direction of the various types of corners. (I found the definitions here.) This marker seems to be in the center of a section rather than on a corner, but maybe I am reading the maps incorrectly.

And thanks for pointing me to the PLSS. Although I'm still trying to decode this on the maps I've seen, this part of the Owlsheads are just at the northern part of San Bernadino County. The following image (lifted from Wikipedia's article) on the PLSS, shows grids with perfect squares:

[Image: Systemic_numbering_in_the_Public_Land_Survey_System.svg]

I guess that "S36" on this marker has something to do with Section 36. The weird thing on the Peakbagger map of that area is that there are two sections just south of Lost Lake that are labelled 36, one right above the other. (BTW: I am not sure how to find the original 7.5 minute quad on CalTopo or USGS. I don't expect anyone here to spend time being my tutor, however, I would be grateful if anyone has a link.)

Thanks again!

RE: Benchmarks, survey markers, and maps - DAW89446 - 2024-03-17

(2024-03-17, 10:16 PM)edward Wrote:  (BTW: I am not sure how to find the original 7.5 minute quad on CalTopo or USGS. I don't expect anyone here to spend time being my tutor, however, I would be grateful if anyone has a link.)

I don't have a link; though you could probably find them online. For decades I used the original paper topo maps; but after I collected hundreds, adequate storage became an issue. I still have National Geographic TOPO! map software, with California, Nevada and Utah map sets on CD ROM for my old Windows Vista computer. Then I got a Windows 10 computer and found Google Earth (TOPO! is incompatible with Windows 8 on up). TOPO! used USGS mapsets, but were seamless, so you could go to one quad to another without interruption.

RE: Benchmarks, survey markers, and maps - edward - 2024-03-18

(2024-03-17, 10:33 PM)DAW89446 Wrote: I don't have a link; though you could probably find them online. For decades I used the original paper topo maps; but after I collected hundreds, adequate storage became an issue. I still have National Geographic TOPO! map software, with California, Nevada and Utah map sets on CD ROM for my old Windows Vista computer. Then I got a Windows 10 computer and found Google Earth (TOPO! is incompatible with Windows 8 on up). TOPO! used USGS mapsets, but were seamless, so you could go to one quad to another without interruption.

I imagine that I'm not the only one who still like paper maps! I did find the USGS map here (and seamless on CalTopo here; Base Layers > Scanned Topos). It states that it was "derived from aerial photographs taken" in 1976, "field checked" in 1981, and "photoinspected using imagery dated" 1996. I like the history that the older maps reveal (e.g. mines, old roads, etc.). The benchmark you pointed out earlier on those maps does not show on the newer 7.5 minute maps, but I guess it's still out there.

RE: Benchmarks, survey markers, and maps - GowerGulch42 - 2024-03-18

You can use the USGS's data portal, The National Map, to find all the available USGS maps for a given area. The viewer is at: https://www.usgs.gov/tools/national-map-viewer
and the download portal is at: https://apps.nationalmap.gov/downloader/ They have tutorials on using and accessing data, or if you're having trouble you can send me a PM and I'll help you out.

RE: Benchmarks, survey markers, and maps - edward - 2024-03-18

(2024-03-18, 11:33 AM)GowerGulch42 Wrote: You can use the USGS's data portal, The National Map, to find all the available USGS maps for a given area. The viewer is at: https://www.usgs.gov/tools/national-map-viewer
and the download portal is at: https://apps.nationalmap.gov/downloader/  They have tutorials on using and accessing data, or if you're having trouble you can send me a PM and I'll help you out.

That's perfect. Thank you!

RE: Benchmarks, survey markers, and maps - wyethia - 2024-03-25

Everyone appears to have pointed in the correct direction. PLSS is still in use especially on public lands.  Even lots in town reference back to it if you are willing to read through the survey data long enough, unless you are in a part of the US that was settled before 1785.

Yes the 36 refers to section 36, probably for Township 19N  Range 1E San Bernardino Meridian.  The 1/4 stands for quarter section corner - usually halfway along the boundary of the section. The horizontal line with the section number below it means it is the line between sections 36 (to the south) and 25 (to the north). Looking at my copy of Quail Springs Quad and Edward's clip, there is a jog in the how the corners line up between the townships, plus a township 18 1/2 !  what that means is that due to the curvature of the earth, or poor initial surveys, or both, the square grids don't line up perfectly in this area. Also interesting is that the map only shows some of the sections, which probably means that the PLSS was incomplete, not surprising if most of the land was still in government hands (why pay for surveying something that will never be transferred?) San Bernardino meridian starts on the top of Mount San Benardino and given the bonus township 18 1/2, at 6 miles per township (roughly) that is about 115 miles distant. I am not going to bother measuring that on Google Earth to check my guess.

Anyway, even though I probably have completely bored all of you, corner markers and associated signs are still useful and often historic. I will always stop to look at them.