Some of the best West Texas surveyors in the 19th and early 20th century took bearings to topographic features such as peaks from corners they found or established and noted those bearings in the metes and bounds descriptions they prepared. There were relatively few trees, so they used much more distant, identifiable points that are actually much more useful in helping recover their bearing basis.
Here is a classic example of that. These are two rock mounds, both very early 20th century in origin, from which a surveyor named Nick Thee measured the bearings to three mountain peaks that he described in the record of his work he filed in 1953.
Rock Mound No. 52
Rock Mound No. 53
I found old 60d nails in both mounds that may not have been Thee's. I used each as the center of the mound, though. The nearest peak was more than six miles away, so any difference between where Thee centered his transit and I set up the total station would be quite small. Here is the comparison between the actual grid bearings of the peaks and the bearings that the 1953 surveyor reported.
By the way, as may be seen, nearly the entire tract was very densely vegetated and lots of brush cutting was required. Not.
This is the control point from which the connection to NAD83 was made via OPUS. Two eight-hour sessions gave a wonderful answer.
those innocent looking desert bushes have a nasty habit of puncturing tire sidewalls. 🙁
> those innocent looking desert bushes have a nasty habit of puncturing tire sidewalls.
Yes, those creosote bushes (aka greasewood) break off and make sharp stubs that will definitely go through a side wall. I keep my driving through them to a minimum. Walking is easier.
To get to those two rock mounds was only about a mile and a half hike, although carrying a heavy pack and the necessary climbing to negotiate arroyos made it seem a bit longer.
For the record, this was the feature in Mexico that was described as "East peak of 3 peaks".
By the way, in case anyone is wondering how to point on a fairly coarse topographic feature like a peak, the answer is that you point the telescope at the high point of the peak unless the description mentions otherwise. This is when you are following a transit survey.
One exception is where there was a triangulation cairn built on the peak prior to the surveyor's work that is being followed. Usually, those bearing calls read something along the lines of "monument on Mt. St. Andrews" or something line that.
David... And they also have a marked preference
for brand new tyre walls to spike....
RADU
What is the grid convergence angle?
> What is the grid convergence angle?
At Rock Mound 52: -2°33'45"
At Rock Mound 53: -2°33'44"
Mr. Thee's bearing basis was only approximately true North. This was why determining the actual North direction he was using was important in reconstructing the boundaries established by his 1953 work.
Mount Rainier was used quite frequently. There is a big waterline that heads toward the big mountain for a couple dozen miles.
It's a poor picture, but you are looking right at Mt Rainier.
Cheers,
Douglas
> It's a poor picture, but you are looking right at Mt Rainier.
I'll bet that's what all the real estate agents say.
Kent McMillan, Texan, age 37. Cannot return to his home. The reason is a little vague. We also know what convergence angle you used in West Texas, Mr. McMillan, and also we know why you left Austin.
By the way, on the subject of index errors, I found that the North line of the piece of school land that Nick Thee reported as running Az.90°00'00" (actually, his call was East) ran Az. 92°08'14" (Grid). It turned out that Thee had located the corners that defined the line by connecting them via random traverse, not by running the line itself.
On the lines he actually traversed, his index error was remarkably consistent.
While stationed at Luke AFB in 1975-6, we bivouac at a crash site some place south of Flagstaff. We used surrounding peaks as targets for a dead reckoning kinda approach for a location from observed intersecting bearings estimated from quad sheets and using an old transit - rough triangulation.
It got us close enough to make a crash site map with a good approximation of the position for the brass.
We also used this technique out in the desert down near Gila Bend.
dla
> We used surrounding peaks as targets for a dead reckoning kinda approach for a location from observed intersecting bearings estimated from quad sheets and using an old transit - rough triangulation.
Sure, in the days before handheld GPS gadgets, using quad sheets to navigate was the main method of getting close enough to look for corners. You plotted the surveys on the quad sheet, or at least where you thought they were, using whatever calls in the record tied the work to the ground and then walked to the vicinity. A plotted intersection of compass bearings from two features or a three-point resection with a compass would do the trick if there were no other terrain features nearby.
That is how I was taught to navigate on the quad map on backpack trips in the Sierra Nevada in the 1970s.
Sight several peaks shown on the map with a compass, lay the map on the ground, large rock or log, orient it to north then plot the lines with the compass. Where they intersect is roughly where you are. It works reasonably well especially if you are familiar with which peak is which.
In the airplane you can take bearings off of VOR stations (VHF Omni Range) and plot your position on the Chart. The VOR symbols have a compass rose surrounding them so no need to orient the map.
The difference is that you are resecting with angles measured to the peaks, and VOR is giving you a triangulation with angles (azimuths) from the stations to you.
For some reason it really gives you a good feeling navigating like that.
The other important aspect of using maps in the mountains is the elevation. If you bring an altimeter, many times you can find yourself on a map using a single bearing and a contour line. Quads have UTM ticks that can be used with GPS.
If I were to stay an extended amount of time in the mountains, I would bring a plastic coated quad map, scale stick, a good compass, and lastly a barometric altimeter (no batteries).
As a back up I'd bring a modern hand held GPS and extra batteries 😉
JRL
> If I were to stay an extended amount of time in the mountains, I would bring a plastic coated quad map, scale stick, a good compass, and lastly a barometric altimeter (no batteries).
A guy I used to work with had a degree in Geology from WWU in Bellingham. While he was still in school he worked a couple summers for the US Geological Survey in the North Cascades, verifying existing Geological maps, in the the mid 1980's. A chopper would drop him and another guy off for weeks at a time. All they had to navigate with was a copy of the existing Geo map, a scale, a compass and barometric altimeter.
He had lots of good story's:-D
Cheers,
Dugger
