This tale is kind of long, and it's just beginning, so first a little background:
In 1881 USC&GS surveyor George Davidson measured the Yolo Base Line to anchor the western end of the 39th Parallel Survey, a triangulation network that eventually spanned the continent. The Yolo Base Line is considered the most accurate base line measured in the 19th century, and some novel apparatus and techniques were used in its measurement. Its southern terminus is about 3 miles from where I live, on agricultural/riparian land owned by the University of California.
I've been aware of the line for the last 20 years or so, have visited both terminal monuments several times in that span, have skimmed some of the pertinent documents, and have always had it in the back of my mind to dig deeper into its history. But I never quite got around to doing anything about it until a phone call came in out of the blue last week. The caller was a lady who's a history enthusiast. (Monica B., if you're reading this, that's you!) She heard about the line and became interested in writing a book about it. She got my name somehow, and called to ask if I could shed any light on the matter, particularly helping her interpret some of the terminology used in the historical record. That was enough to revive my interest in the subject.
I reviewed a couple of the USG&GS reports, and -- reading more closely this time -- saw that the Base Line measurements included stones set at every full kilometer of the 17+ km line, plus 9 "fence stones," presumably set wherever the line encountered a fence. (I haven't yet located a detailed description of either the kilometer or fence stones, but I have a lot of reading to do yet.) The 1883 Report of the Superintendent of USC&GS shows the measurements to these stones:
(The text is a bit hard to read here, but for those interested the report can be found on this page.)
Although the positions of these intermediate marks aren't in the NGS IDB, the endpoints of the Line -- YOLO SOUTHEAST BASE (JS4578) and YOLO NORTHWEST BASE (JS4571) -- are. Last night I took the published positions of the endpoints and, using the distances shown in the table above, calculated positions for the intermediate points. I loaded these into the Triumph-LS that I have as a demo.
This morning I went into the field. First I visited YOLO SOUTHEAST BASE, both to get a couple of photos and to make sure I got the coordinates loaded correctly. (I hadn't, as it turned out -- not sure what happened, but I had to run back to the office to reload them.) Here's a photo of the tower that was built over the mark sometime prior to 1927:
(The disk in the side is a bench mark that USGS installed at some point.)
When I first saw this monument in the early '90s, it had a rickety and heavily-weathered 2x4 railing jury-rigged around the top. Evidently someone in the pre-GPS days had occupied the top mark with an instrument.
I'd never seen the top, though, so today I climbed up. I didn't have a ladder in the truck, but I did, of course, have a surveyor's stepping stool:
Here's a shot of the mark on top of the granite monument:
And the view from the top, looking generally toward YOLO NORTHWEST BASE:
While I was there I also recovered one of the nearby RMs, then headed off in search of intermediate stones.
The Base Line is, for the most part, heavily cultivated, so I'm skeptical that the full-kilometer stones have survived. There may be exceptions, but for today I decided to concentrate on the fence stones.
The first one going northwest falls, according to Google Earth, in a heavily-used county road, so I didn't bother looking for it. The next one, though, looked promising -- Google Earth indicated that it fell very near an existing fence. I drove up to the site, pulled out the RTK unit (connected via IP to CSRC RTN station UCD1), and staked out the position. Setting the receiver aside, I pushed a probe into the ground and got a distinctive *tink* just a few inches down. Assuming this to be a rock, I grabbed the shovel anyway and started digging. It was, in fact a rock, but it was this rock:
I took an RTK shot on it, and later calculated it to miss my record position by 3 cm for distance and 14 cm for line. Ridiculously close, given the many error sources at play.
Alas, my initial success was not to be repeated today. The location at the next fence stone offers a modest possibility, but the ground was too hard to probe more than an inch or so. (We need some rain!) The next one after that is on private land, so I want to contact the owner before poking around. And the last one I tried to day was another possible-but-unprobe-able situation.
I spent pretty much the whole day on this volunteer project, and I don't know when I'll be able to get back to it. But having channeled Jerry Penry all day, I think I have the bug.
P.S. For a detailed description of the base line measurement apparatus and its application, see the Report of the Superintendent for 1882 from the site linked above.
> P.S. For a detailed description of the base line measurement apparatus and its application, see the Report of the Superintendent for 1882 from the site linked above.
I'm sure you've seen the photos in the holdings of the Bancroft Library showing various details of the measurement of the Yolo Baseline. Here's the baseline party measuring to one of the Fence Stones.
The men of the Base line survey (Dave Karoly at rear, looking toward where he left the tardis):
Yes, I've saved the Bancroft photos, and also have this one from an NGS PowerPoint that Monica B. sent me. It purports to show the bars in use, though it would appear to be from a different era judging from the clothing:
Yolo Base Line 1881 - Telegraph Wire
One interesting detail is how the preliminary baseline stations were laid out.
From Page 142 of the 1882 Report:
>When I was occupying the stations Southeast base and Northwest base with the large theodolite, Assistant Colonna was detailed to run a line of levels and repeat between the two stations, and then to connect the Northwest base with the California Pacific Railroad bench-mark at Woodland. Fifty-metre telegraph wire was compared with a Chesterman steel tape on top of a straight level fence.
>In measuring, the ground passed over was either high stubble or summer fallow. The wire was strained 48 pounds by a spring balance at the forward end. A stub was driven in the ground at every 50 meters and a tack driven in top of the stub.
I have to wonder how commonly ordinary wire was used in late 19th-century surveying practice instead of chains.
The gentleman seated on the far of the frame right appears a little bored. His dress doesn't appear to be as crisp as some of his colleagues, and his shoes are not as bright.
hmmm....
By golly, I believe they had a surveyor on the crew! B-)
So cool. Those precise baseline measurements from that era are always so fascinating to me. Retracing one sounds fantastic. Be sure to watch for the scratch mark inside the punch mark when you get a shot.
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> hmmm....
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The caption says "Yolo Base Line Party". Doesn't look like much of a party... I don't see a single bottle 😉
That instrument in the photo appears to be Eimbeck's Duplex Bars. I still maintain that some of these baseline measurements of a century ago are MORE accurate than what GPS can give us today.
Here is an article I wrote about the world's most precise instrument in my opinion - Woodward's Ice Bar.
http://www.amerisurv.com/PDF/TheAmericanSurveyor_Penry-WoodwardIceBar_April2007.pdf
Here is another baseline in Nebraska where I recovered the end points.
http://www.penryfamily.com/surveying/pagebaseline.html
After the article was published, a surveyor continually engaged me for not getting GPS positions on the end points to see how 'close' the USC&GS surveyors were in comparison to GPS as if GPS is infallible. How these guys measured a century ago cannot be compared to modern GPS and I would personally go with their results over GPS.
I like your thinking Jerry.
> How these guys measured a century ago cannot be compared to modern GPS and I would personally go with their results over GPS.
This will be a great test of the accuracy of the Javad GNSS receiver that Jim has, then.
> This will be a great test of the accuracy of the Javad GNSS receiver that Jim has, then.
I've thought about occupying both ends of the base line, but I'm not sure the result would be worth the effort. First, because the existing granite towers are 8 or 10 feet tall and relatively narrow at the top, the setups would be tricky, involving ladders and custom tripods. Second -- and this is the larger issue -- I have no way of knowing whether the top marks are still plumb over the original surface marks, so the measurement would be inconclusive.
> > This will be a great test of the accuracy of the Javad GNSS receiver that Jim has, then.
>
> I've thought about occupying both ends of the base line, but I'm not sure the result would be worth the effort. First, because the existing granite towers are 8 or 10 feet tall and relatively narrow at the top, the setups would be tricky, involving ladders and custom tripods. Second -- and this is the larger issue -- I have no way of knowing whether the top marks are still plumb over the original surface marks, so the measurement would be inconclusive.
Didn't the report detail reference marks at the ends of the baseline, offset from the pillars?
> Didn't the report detail reference marks at the ends of the baseline, offset from the pillars?
Yes, but only the closest two of the original RMs at YOLO SOUTHEAST BASE -- one north and one east -- have ever been recovered, and that was in 1931. At that time the north RM was only 6 inches below ground. It *might* still be in place, though it would be in a dirt farm road if it is. The one to the east was described as being 3 feet below ground in 1931, and it's probably still in place, but that's a lot of digging. The more distant original RMs have never been recovered; both are in heavily cultivated fields that may have been ripped. I rate their survival prospects as iffy.
The RMs at YOLO NORTHWEST BASE are more challenging, as the monument sits in a developed cemetery. A Google Earth image of the site shows the granite tower in the center of the crossing pathways:
Even if the RMs survived development of the cemetery, I don't think any hole-digging would be appreciated.
Here's an image showing a small portion of the 39th Parallel triangulation network, with the Yolo Base Line shown as a heavy line in the lower left quadrant. The length of the base line in relation to the extent of the triangulation -- and this is just a tiny bit of the network -- illustrates the reason so much effort was put into accurately measuring the base lines. The small errors in base line distance measurement got magnified many times as the triangles spread across the land.
This is great stuff. I have always been very interested in the old triangulation network and baselines. We recovered station BETHEL (PID JU3319) in 1993 while doing a bluebook survey for the City of Philadelphia. It was a cone about 2 or 3 feet down, the surface station was gone. It apparently hadn't been used since 1880, but checked well (NAD83 86) with other triangulation stations.
The City of Pittsburgh Geodetic Survey done in the 1900's to 1920's had ten baselines in the network. I recovered a few single baseline stations, but only one intact line (BASE 10).
These lines were measured at least six times each, with a different tape each time. This is discussed in a report about the survey, starting on page 7 of City of Pittsburgh Geodetic Survey
What is interesting about this network is that if you look at an NGS control diagram, there are measured baselines shown between USCGS triangulation stations in Pittsburgh. Now, if you have ever been to Pittsburgh you would know that it would be impossible to measure between those stations without an EDM. Yet those baselines were used in the NAD 1927 adjustment. The guy who designed/implemented the network in Pittsburgh later went on to USCGS. They decided to use COMPUTED distances from the City triangulation as MEASURED distances in the national network. I was told many years ago when I inquired about this that it was the only place in the country that this was done, i.e. using distances computed through a network as "measured" baselines.
Thanks Jim, this is fun stuff. I'm interested in another side of this too. How do the “fence stones” fit present day fences, and (for whatever reason) might these fences ever have been accepted as boundaries? These questions come to mind because on a current project we have a fence location that purportedly dates back to 1873 (but have no “fence stones” to help us prove it!). Multiple contradicting GLO surveys, and lack of evidence today from those surveys, have us looking at the “1873 fence”. I get the feeling that out in the central valley you work in it’s not unusual that there would be a lack of GLO evidence, leaving fences as the best evidence.
Chris
Ah ha!
Just take a run out there on Halloween night and do your observations.
Interesting project even if it is a volunteer effort.
Read about Carolla in American Surveyor Mt. Shasta Triangulation article.
Do you have copy of the sketches from the Superintendent's report.
A lot of the scans from University libraries and other sources fail to scan the sketches.
> Do you have copy of the sketches from the Superintendent's report.
The only sketch from the report on the Yolo Base Line is this detail of reference marks:
There appear to have been at least 5 more, but I don't know what happened to them. This one is from the PDF I got on the NGS site.
very interesting. While not of the length or importance here is one from NY of about the same era. If you click on the notes it is an interesting read.
Jim
http://www.colvincrew.org/archives/355
Fascinating. Good job Jim. I can't wait to see more posts about your progress. Thanks.
