• Dale Hill

GPS on Bench Marks - June 2021

Updated: Jul 8

Ramping up


I decided to ramp up my planned recoveries for the GPS on Bench Marks Initiative after last month, with the ultimate goal of reaching 100 submissions before the program ends in December. That's an aggressive target considering that I am currently sitting at 27 GPSonBM recoveries, meaning I'll need to do a little better than 10 qualifying recoveries per month from now to the end of the year. Being side-lined from hiking with a knee injury this past month has afforded me the opportunity to focus more on these priorities and my 9 recoveries this month reflect that.


Citizen Science and Crowdsourcing

GPS on Bench Marks is the National Geodetic Survey's crowdsourcing approach to obtaining survey-grade GPS data on a prioritized list of marks where new data will provide the most benefit. Surveyors, engineers, and technicians that work for Federal and State government agencies, universities, professional societies, and private sector firms use their GPS equipment to take measurements on survey marks in the areas where they work and share them with NGS via our online tools. The public can also participate by finding the survey marks on the priority list and reporting back to NGS on their condition and suitability for GPS observations. This crowd-sourced data helps to improve the local accuracy of national scale models and tools that NGS builds to serve the Nation.


Jump to a Mark...

  1. DX5297: SAN DIEGO GPS 03 (Fallbrook, CA)

  2. DC1434: E 1415 (San Diego, CA)

  3. DC2133: SAN DIEGO GPS 23 (Point Loma, CA)

  4. DX1167: OC 140 (Encinitas, CA)

  5. DX1173: OC 145 (Encinitas, CA)

  6. DX0471: 11 AAR (Borrego Springs, CA)

  7. DX0474: CL 30 (Borrego Springs, CA)

  8. DX0441: AD 29 (Thermal, CA)

  9. DX0449: G 517 (Thermal, CA)


June 6, 2021 - CA 76, Fallbrook, CA


DX5297: SAN DIEGO GPS 03 (10 km, Priority A-1 Observation)


Just a week after my slip and fall in the desert, (and what would end up being a completely torn ACL), I planned an afternoon trip to recover a collection of GPS on Bench Marks priorities along SR 76 between Oceanside and Bonsall. The main criteria for my targets were that they had to be close to the roadside and require minimal hiking to reach them. Using the GPSonBM Map, I identified a half dozen "A" Priority marks and noted another half dozen regular NGS listed survey marks that appeared to be easy recoveries on my driving route.


Of the dozen marks that I had on my list for today, this was my only recovery, and as you can see from the marking on the sidewalk and bridge abutment, this was an easy one to locate. I've recovered quite a few California Department of Transportation marks but this was the first one that had dual stamping. The first stamp NE 15/76 1980 identified it as being northeast of the point where the bridge of SR 76 crosses over the 15 Freeway. The second stamp SDGPS03 1991 identifies it as the GPS station.


Even though I only found this one mark on today's outing, it would be the first of five that I would find this month that was mounted on sidewalks, on bridges, or on wing walls. Wing walls are usually attached to bridge abutments and act as retaining walls and may be straight or fanned out depending on the surrounding terrain. On bridges that go over waterways, they are generally splayed to channel the water under the bridge. On smaller bridges, for example, those over train tracks, the wing walls tend to be straight. The last mark I found this month in Thermal was located on a wing wall.



June 12, 2021 - West Morena Blvd., San Diego, CA


DC1434: E 1415 (10 km, Priority A-1 Observation)


The last part of my pre-trip planning for today's SMASH was to see if there were any survey marks listed on the GPS on Bench Marks priority map near where I would be throughout the day. To my surprise, there were only two!


I added the Vertical Control Mark, station E 1415, to my list for today and made a note that SDGPS 23 would have to wait until I returned to Cabrillo National Monument since it was inside the Park. E 1415 brings my GPS on Bench Marks submissions to 18. I think I need to plan a SMASH trip dedicated solely to GPSonBM marks!

Note: This was part of my June 12th SMASH - Survey Mark Scavenger Hunt


June 19, 2021 - Cabrillo Memorial Drive, San Diego, CA


DC2133: SAN DIEGO GPS 23 (10 km, Priority B-1 Observation)


This recovery was on a return visit to Cabrillo National Monument to pick up my FREE Annual National Park pass for Military Veterans 😊👍This recovery wraps up the two GPS on Bench Marks priorities located in San Diego


June 25, 2021 - Encinitas Blvd, Encinitas, CA


DX1167: OC 140 (2 km, Priority A-2 Observation)


Three weeks post-injury, I was getting a little stir crazy sitting around the house so I planned another GPSonBM trip along the Coast between Encinitas and Oceanside. There are a good number of priority marks in this corridor, however, many of them are located near the train tracks in the Los Angeles to San Diego (LOSSAN) rail corridor which is owned and managed by the North County Transportation District. For safety reasons, access to the tracks is restricted, and in many locations, it is completely fenced off. Of all the marks on my list that were near the railway, this was the only one that was practical to recover as it was just up a small embankment from a dirt parking area and I had good visibility down the tracks in both directions.


June 25, 2021 - N. Coast Highway 101, Encinitas, CA


DX1173: OC 145 (2 km, Priority A-2 Observation)


This was another easy 'sidewalk' recovery, when I looked it up on the map, it was about 25 feet from a Real Estate office that sat kitty-corner on the Coast Highway. I initially pulled into their parking lot and started over to the bridge when an employee came out and told me I couldn't park there. I explained what I was doing and that I'd only be there 3 or 4 minutes max, he held firm (despite the completely empty lot!). No problem, I drove across the bridge and down a side street and found free on-street parking. I hiked back to the mark, made the recovery, and on my walk back to the truck found a North County Transportation District Control mark in the middle of the sidewalk directly over the tracks! I would never have made that recovery if I'd been allowed to park in the lot, so perhaps the guy being a jerk was fortuitous 🤣 (you can read about that recovery, N.C.T.D. STATION CONTROL MONUMENT 2007, in my June Drive-By post)


June 27, 2021 - Henderson Canyon Road, Borrego Springs, CA


DX0471: 11 AAR (10 km, Priority B-1 Observation)


Normally at this time of the year, I'd be well into my heat acclimation training hikes in the desert, but just about a month after my ACL injury hiking in the Borrego Badlands, my return to the desert was focused primarily on GPSonBM recoveries that I could drive up to. I organized a full day of survey mark hunting activities around this mark, it was the first priority mark near or on the Borrego Salton Seaway and SR 86 that paralleled the Salton Sea.


As it turned out, I would also have a very successful day with Drive-By Recoveries along this same route, but those are included in a separate post. This mark was located near the California Historical Monument for Peg Leg Smith, just off of Henderson Canyon Road, it was also very close to a Section Corner mark that was a cool recovery.


This is a Federal Base Network Control Station and the first mark I've recovered that is part of that network. The Federal Base Network (FBN) is a nationwide network of permanently monumented stations spaced 100 kilometers apart with higher density in crustal motion areas. The FBN provides spatial reference control that has some of the most precise accuracies available today.

June 27, 2021 - Borrego Salton Seaway, Borrego Springs, CA


DX0474: CL 30 (10 km, Priority B-2 Observation)


I think the desert has the highest percentage of undisturbed witness signs that I've encountered! I made a lot of Drive-By Recoveries today just by keeping an eye out for these standard witness signs. Of course, for the GPSonBM priorities, it made finding those much easier. I had three on my list that were all S.D. County Engineer Dept. discs mounted in a 5-inch concrete pipe, you can see that for this one the pipe is pretty much destroyed, but the mark was still in good shape.


I did have one on my list where I found the witness post knocked over, the sign was torn off, and there was no evidence of the concrete pipe or survey mark. It appeared as if the area had been roughly graded and the mark was destroyed in the process.

June 27, 2021 - Borrego Salton Seaway, Thermal, CA


DX0441: AD 29 (10 km, Priority B-2 Observation)


This one is a good example of an intact monument (concrete pipe), marker, and witness sign with a bonus T-bar fence stake as a second witness stake.


June 27, 2021 - CA-86 North, Thermal, CA


DX0449: G 517 (10 km, Priority B-1 Observation)


While not the last mark on my target list of recoveries, it ended up being my last recovery for the day. I had three more marks that were further up the road on SR 86, but the air conditioning in my truck decided it was time to quit working. It had started blowing hot air well before I got to this mark, but with outside temperatures around 120º I couldn't keep my iPhone cool enough, shortly after taking these pictures my phone overheated and I wasn't able to cool it down until I got home.

The mounting for this mark is a good example of wing wall mounting. Fortunately, with the heat, there just weren't a lot of people out on the roads so it was easy to pull off on the road into the median near this little bridge to safely make the recovery. I suppose I'll head back out there again to make the remaining recoveries, perhaps in conjunction with a SMASH around the Salton Sea (there are TONS of survey marks out there!)


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