Decipher 1985 Field Notes

He's reading Zenith angles, not vertical angles. And he's reading both faces.

With Zenith angles, 0° is straight up, 90° is horizontal, 180° is straight down, and 270° is the other horizontal.

And in looking them over some more, I don't think he was reading both faces. After he read a Zenith angle with scope inverted he subtracted to get the other zenith angle because that's what his trig tables or calculator required. Ni I-man is going to get perfect checks every time.

It appears that they were closing the ZA as a check. A ZA of 270 would be level with an inverted scope.

> He's reading Zenith angles, not vertical angles. And he's reading both faces.
I think that he is reading zenith with the telescope in the reverse face, then writing the zenith converted to the direct face reading in parentheses.

Instruments read in either zenith or vertical angles when measuring slope angle.

Zero on a zenith scale was pointing straight upwards that presented level readings of 90deg for direct readings or 270deg on indirect readings.

At level, Vertical angles are at a reading of 0deg or 180deg.

B-)

> I think that he is reading zenith with the telescope in the reverse face, then writing the zenith converted to the direct face reading in parentheses.

I'm having some difficulty imagining why the zeniths were read only in Face 2 position unless the EDM was telescope mounted and that prevented the telescope from transiting (being plunged or reversed).

Thank you all for explaining the vertical angles. That makes sense. I had focused so much on the angle that I didn't figure out the distance. I was taking the difference between the two distance next to the horizontal angle and vertical angle to be the rod int, but I'm not sure that's working after all. Is there a better explanation for the distances?

thanks again,
Dustin

I agree. We had a Wild with DistoMat when I was a lad and you could only shoot upside down and backwards.

Since the notetaker was recording Zenith angles, it's safe to assume that all the distances are slope distances and need to be reduced to horizontal.

It looks as though the distances along side the horizontal angle are the horizontal distances and have been reduced from the zenith angle and the slope distance.

You should be able to create what ever points you are trying to create by the HA and HD on the same line. Simply use a dummy backsite of 0° and 100' (or whatever) and turn the angle and distance listed on each line. It looks like you might have to do some renumbering though.

Do The Math

The distance on the zenith line is slope, use the sine of correct zenith and you get the horizontal distance which is written on the horizontal angle line. The lower line distance was written before the upper line distance.

Paul in PA

The Earlier total stations could report slope horizontal and vertical distances by pressing buttons.
I believe those notes were taken with an inverted scope, and the direct zenith angle and horizontal distance were calculated. I don't see a backlight check unless the reference to pg 3 is it. My first concern would be the backlight, the rest is academic.

Do The Math

There was no need to calculate the reciprocal of the F2 zenith angle. Sin 89 is the same as sin 271 except the signs are reversed. So just use the absolute value of sin 271 🙂

Hey, I made lots of 1985 fieldnotes, which have stood the test of time. These fieldnotes, without the accompanying book, are not so good.

For starters, if this is spread one of the day's work, there should be a date, crew positions, equipment used and a weather note on the upper right hand corner of the spread. In more modern times, file names, etc. Also, that drawing on "page" 3 should be a dilly to explain what he/she's doing here with all the extra integer notations, apparent perfect F1-F2 VA results, etc. There's no column headers to describe slope vs. horizontal distances, etc. The format on this page sucks.

It's not stadia, because an upper hair-lower hair pair would have been recorded in addition to the VA to deduce the distance. Or, if using a subtense bar, an angle to left target and to right target (much more accurate at high vertical angles), although at the time a subtense bar was pricey and delicate.

Having been a fieldman in that era, transcribing that much stakeout data over the phone made me nervous, a particularly tedious procedure of listen and write down the angle, recite it to the sender who says "check", then similarly the distance, etc. Much preferred getting a fax at the contractor's office, or a runner, or an actual mag-card or tape upload from the office at the start of the day.

Why the angle-distance stakeout info from the "low bank" setup, where he's setting iron? Much more common in 1985 was providing coordinates so the party chief could setup on whatever control he wanted to and use his trusty HP41CX to develop angle-distance stakeout info, or even, perish the thought, punch the coords into a total station for stakeout. Then, setup on the opposite side of the job and shoot the irons to look for busts.

He/she then switches to some topo collection (or stakeout?) of a small feature about 100-200' away, the mysterious "R" points. I'd like to see spread one and three before pontificating on WTF's going on there. Curious is the angles are exactly divided into 1/10th (6") of a degree which implies an older Gurley type transit, and all distances are tapeable. The super high angle accuracy iron setting angles came from the office, unless he/she did multiple rounds without recording the reduction calcs they are bogus. This could be a case of ancient equipment field observations getting typed into some sort of point number based primitive computer later and respewed.

If he/she's using an old 1' transit (estimation to 1/10th second) and steel tape in fairly flat land (based on VAs) is the survey outperforming RTK? The interpositional distances are only 200'. Ruminate before answering, pundits. Consider this survey may have been in heavy tree canopy and was the most professional way to conduct the survey.

I'm guessing a Wild T1 (6") with scope mounted EDM. The Distomat counterweight was down in Face2 so our Party Chief would take topo like these notes except he would note HIs and rod heights.

> I'm guessing a Wild T1 (6") with scope mounted EDM. The Distomat counterweight was down in Face2 so our Party Chief would take topo like these notes except he would note HIs and rod heights.

It doesn't seem these fieldnotes are useful for determining relative elevations, only relative position.

Used a Kern Distomat DI3S and got amazing results over short distances, as good as levelling. Over thousands of meters, not so good. The inversion of the counterweight and optical ground shimmer D2 long range observations messed up the VA rather severely. Fixed by simultaneous VA observations at the target with a second Kern theodolite on station. We could get results less than 0.5' over several kilometers with a 3000' foot elevation change. Good enough for the road builders. Strange guys, they were building a road on a steep escarpment, and were overjoyed when our numbers were roughly correct (they were building the road from the top down and the bottom up simultaneously) and very happy with our horizontal alignment connection. They did pop us for the 0.3' vertical error upon the join, 1500cy of additional earthwork for $3000, which we gladly paid on a $90,000 contract.

Edit>> meant 1/10 minute, not 1/10th second, which would require geodetic optical equipment.

At Station R#5(139)
The reduced vertical angle is suspect.
VA 269°05'00" (99°55'00")
Should be (90°55'00")
The reduced horizontal distance has been computed correctly.

"Having been a fieldman in that era, transcribing that much stakeout data over the phone made me nervous"

[sarcasm]Man! You're not kidding. I think that's about the time phone calls went from $0.10 to $0.25[/sarcasm] 😀

No clue here. Possible chief got read the azimuth and distance over the phone for one side of an even width and parallel ditch, took the 41, assigned arbitrary coordinate values then rolled with the stakeout ?

Eight assigned azimuth and distance, two of which appear to be control (according to the scant description) leaving six "iron rods set".

Page break

Occupied two backsighting one and record twelve "R" sideshots. Is that six irons for the low bank on both sides of a ditch ??
If they kept the flopped scope throughout the stakeout, the sideshots should be comparable ??

nm, math doesn't seem to work for that assumption. I have no idea