• Dale Hill

Mount Pinos Survey Marks

Updated: Feb 14

Today was a great hike in the snow to summit three peaks, Mount Pinos, Sawmill Mountain West, and Sawmill Mountain. As is my goal this year, I am revisiting peaks that I have previously summited and trying to recover more, if not all, of the survey markers that I may have missed on prior trips.


The Primary Station is a standard 3" brass triangulation station disc stamped "MT PINOS 1941"

The associated Reference Objects are listed below.


Here's the recap of the day's efforts, clicking on a heading will take you directly to that section of this post.


Today's Recoveries

  1. EW7674 Mount Pinos Triangulation Station *

  2. CC2249 Mount Pinos Reference Mark 2

  3. CC2250 Mount Pinos Reference Mark 3 *

  4. EW7675 Mt Pinos USAF Tower *

  5. Section Corner Township 009N 021W, Section 31, SE Corner

Confirmed Lost/Destroyed Marks

  1. EW7673 Edwards AFB RAD Relay Annex Tower

  2. EW7676 MP 6 *

Unable to Locate

  1. CC2247 Mount Pinos Azimuth Mark

  2. EW7672 Benchmark 8862

  3. CC2248 Mount Pinos Reference Mark 1

Notes: * previously identified on June 1, 2020


Today's Recoveries


Today I verified that three survey markers or reference objects I located last year were still in place. Additionally, I located two marks that I previously had not found.


Previous Recoveries

New Recoveries


Mount Pinos Reference Mark 2 (PID: CC2249)


Once I knew where to look, this reference mark was remarkably easy to find, it's in great shape and was plainly visible. I am confident that the only reason I didn't find it last year was that I didn't know to look for it. Usually, my trail buddy Curious George comes out for the photographs with new Triangulation Station Discs that I locate, but since this was the only new standard brass disc marker I found today, he settled for that!

Section Corner Township 009N 021W, Section 31, SE Corner


My second new find for the day was unexpected and I almost walked right past it. We were hiking east towards the base of Mount Pinos on our way back from our day's adventure to Sawmill Mountain when I saw a yellow blaze on a tree just off the trail. Upon closer inspection, it was a standard US Forest Service Location Poster (USFS Sign no. 54-5) nailed to the tree. This isn't the first location poster I've found as these are used throughout the National Forests to identify boundaries.

While much of the sign is rusted out, you can still make out enough of the scratched in information to identify the section. Amazing that this poster was set on October 31, 1960, and is still holding up!

The USFS uses two different forms of the Location Poster, one that is pre-printed with the section numbers on it, and one that is blank. The number sequence of sections is standardized, this is an image of the pre-printed sign from the UNICOR Federal Prison Industries website.

These are 4 ½" x 5", aluminum signs. The surveyor would typically use a nail to scratch the pertinent information onto the sign and then would drive the tack (nail) into the appropriate location on the grid to denote what section it identifies. On the image of the actual sign above, I put a red circle around the nailhead that marks the location.


Pre-planning to Locate Corners


I typically review my planned route using the GAIA website on my iMac with the USGS Topographical Map and Public Land Survey System (PLSS) Grid overlays. The topo map will let me see my route, the terrain, and any relevant symbols along the way. The PLSS grid essentially breaks most of the country down into a system of 'Townships' each 36 square miles, the townships are further divided into 'Sections' that are 1 square mile each. The division of each section continues down to quarters and quarter-quarters.


A section is 640 acres, a quarter section 160 acres, and a quarter-quarter section is 40 acres. (in case you've ever wondered where the term "South Forty" came from, this is it!) Public boundary surveys usually only go down to the quarter-quarter.


The first image is an overview of Township 009N 021W, the cyan track in the lower left of the section is my GPS track from today's hike, (the light green track is the route I took on my June 1, 2020 hike).


The second image is an enlarged view of the spot where I located the section mark, you can see that the spot where I found it doesn't fall neatly on the grid system, that's one thing that makes these somewhat elusive to find.


The final image is a snippet of the Topo Map Key that shows the different symbols specifically related to different types of corners that you might find on a map. If the gridlines simply intersect, with no specific legend notation, there may not be a mark set, this particular corner is a good example of that, but just because it's not noted on the map, doesn't mean there's not a mark there. This particular one is a good example of that.


Confirmed Lost/Destroyed Marks


I use the category of confirmed lost or destroyed marks is reserved for those that are clearly gone and are differentiated from those that are just difficult to locate. The NGS Bench Mark Reset Procedures are guidelines to preserve elevation data for a soon-to-be disturbed or soon-to-be destroyed benchmarks. This manual provides instructions for surveyors to preserve elevation data when the destruction of an existing mark is anticipated. Unfortunately, this doesn't account for acts of vandalism where marks are taken as souvenirs.


The National Geodetic Survey (NGS) does not identify benchmarks as destroyed in its records without definitive proof of the mark’s destruction, which usually means physically returning a disc to the NGS (for example in the case of a mark that will be destroyed due to construction activities) however, from a surveying perspective If the old benchmark is in poor condition, such that the elevation may be questionable, it should be considered destroyed and other measures should be taken to establish a new vertical control point.

I have reported marks as lost or destroyed using the NGS reporting tool when it's pretty clear that someone made off with the mark, for example when I located the Ball Benchmark in La Jolla, the concrete-filled pipe that Reference Mark 1 was mounted in was removed from the ground, laying on a side-hill nearby and you could see that someone had used a hacksaw to cut the disc off the stem. Obviously destroyed.


Today I have two that fall into the Lost/Destroyed category, the first is a Gravity Station mark that was obviously removed from its concrete base, the other is more a case of 'double reporting' or someone not doing all their homework before identifying a mark.


Station MP-6, Gravity Station Mark PID: EW7676

The NGS has removed this station from its database, as searches for the Permanent ID come up as "not found", additionally there is no longer an icon for the mark on their interactive map, it only exists as a listed Reference Object on the Mt Pinos Station Datasheet (see snippet above) However the clay pipe, with concrete setting and the obvious outline of the hexagonal Gravity Station Mark still exists and sits right next to the Mount Pinos Triangulation Station Disk.

Edwards AFB RAD Relay Annex Tower, PID: EW7673

This is an interesting one, it still shows up on the NGS Data Explorer and the data-sheet is still active, yet this marker as first observed in 1967 is the same tower that was reported in 1971 as EW7675.


I couldn't find any records that the original tower identified in 1967 was destroyed and later replaced with the one in 1971 so it's possible that the person that first observed it in 1971 did not check the records thoroughly to see that it had already been identified in 1967. The coordinates for the two towers are only 2 feet apart, so it's obvious there is only one tower.


I am not sure why the NGS still lists both in their database, but that's the way it is today. I'll call the most current one "found" but actually in surveying, the older, original mark has precedence, so perhaps I have it flipped. Maybe the NGS needs to merge their data on these two and must make one record.


Unable to Locate


These are the ones that frustrate me! 😂 Of course just because you can't locate a marker doesn't necessarily mean it's been lost or destroyed. The coordinates given on the datasheets have varying degrees of accuracy, for example, if you see the term "Scaled" next to the latitude/longitude for a mark, that means it was calculated using a map and was not directly observed.


Through the activities of new surveys or Geocachers recovering marks, many coordinates are updated as either "adjusted" or "handheld" (GPS unit) these tend to be more accurate. Too, you're at the mercy of the accuracy of the original monumentation and recording of the mark.


I have found many marks that were not where the datasheet said they were, that's where the 'hunting' comes into play!


Today, I had three marks that I could not locate, the Mt Pinos Azimuth Marker, Mt Pinos Reference Mark 1, and a USGS Benchmark for elevation 8826. Neither the azimuth nor reference mark had latitude and longitude coordinates as they are considered like auxiliary reference objects, as such the datasheet provides a compass bearing and distance from the primary station mark. (note: Azimuth marks aren't listed with a precise distance from the station, just a bearing, there may be some descriptive text that gives an approximate distance, but it's one of the things that make them all the more challenging to locate)


The USGS BM 8826 did have its own data sheet and coordinates, which I plotted to within 2-feet of the location I determined from the bearing and distance information. Regardless, my calculated locations for RM 1 and BM 8826 placed them both inside the chainlink fence and locked gate that surrounds the tower complex. If I'm back there in warm weather, I'll use my binoculars to examine the bedrock outcroppings around the tower to see if I can at least confirm that there are discs there.


The Azimuth Mark SHOULD have been fairly easy to locate with the bearing and distance information that I gleaned from the descriptive info in the Station Recovery notes. The hillside where it is located was mostly snow-covered today, I spent about 10 minutes checking out all the visible rocks in the general vicinity that met the description (18 x 24" boulder projecting 14 inches) but didn't find it. This will be a good one to look for in warmer weather when there is no snow cover.


Bottom line


I had two new recoveries today, so that's a WIN. I confirmed three previous recoveries and two marks that I consider lost/destroyed. I still have work to do on this one to find the azimuth mark and to see if I can "see" RM 1 and BM 8826 from the outside of the fence.


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