I'm working on troubleshooting a 1970s bunch of CSMs and Plats of Surveys from the 1970s.
There are misclosures and typographical (as with a typewriter) errors all over them, and one of the things I have to understand is how calcs were done in the 1970s.
Can anyone help me out on this?
DMD, double meridian distance
Law of triangles
Slide Rule
Many surveyors reported actual measurements with errors and all.
Typos have always plagued records........
I recently has a neighbor to my client very unhappy with my reasoning and decision making in locating a common boundary.
His deeds had many errors and one only had half of a property description, the west and north boundaries and not the east and south boundaries.
He did not like my calling his lawyer a hack that could not spell or copy a deed correctly.
Anyway, one boundary was shown as 114.66ft for a boundary call of 145.2ft and I had measured as 144.63ft.
The original surveyor was called in and he told him it was a typo in the deed as his records showed 144.66ft..
Neighbor still not satisfied and as I told my client, will never be.
Kind of depends upon "when" in the 70's. There were a lot of technological advancements during that decade. Saw my first hand-held calculator in 1972. Owned a "scientific" calculator with trig functions (sin, cos, no tangent) and a "memory!!" in 1976. Was using programmable calculators (50 steps) by the end of the decade. That's when we could finally calculate to 4 decimals and round to the nearest 3! RPN was the bomb! Could run a traverse with coordinates instead of using lat/dep sheets! Still had to write everything down and key it back in so, yes, lots of room for transcription errors. Only check was to do it twice using two different methods. It was called "checking" your work. A typo isn't a mistake until it goes out the door.
Curta, a book of 8 place tables, they go to 45 degrees as I remember,,,,,
The 1970s cover a LOT of technological advancement (to say the least). from "mostly" analog (Curta, Monroe, Marchant etc.) in the early 70s, to digital (Marchant, VAX, Olivetti, HP) by the mid 70s. I'm sure that there was still significant "hand calcs" (pencil, paper, sine/cosine tables) going on, but it varied quite a bit depending on the Surveyor/Company.
In my personal experience, digital had pretty much taken over by 1975 or so, although "we" were still doing quite a bit of HP41 calcs even to this day.
Loyal
In our office from at least the late 1950s the primary traverse was comp'd and adjusted by mainframe computer then the side ties were hand calculated from the adjusted coordinates. The calculations of mon set coordinates followed a convenient progression which would accumulate rounding errors which is why sometimes the maps don't quite calculate out the same way or quite close as well as we expect.
The traverses are by double deflection angles by transit then taped distances. The bearings were calculated from the deflection angles then the horizontal distances calculated and that was written on a form to be sent to data processing. Then sometimes they would use the initial output to figure the rotation to the basis of bearings and sent through again, maybe the next night.
I've found things like the calculated bearing from control point to mon set was in the wrong quadrant which explained why the mon was set 5' out of position. I found the control point left there in the 1970s, an 80d spike and the backsite is a tbar about 1300 feet away. I have another one which is just weird...I have his closure calculations but the sheets of legal paper with the calculations where he developed the missing corner coordinates is missing from the file so I can't really figure out what happened.
wfwenzel, post: 424753, member: 7180 wrote: I'm working on troubleshooting a 1970s bunch of CSMs and Plats of Surveys from the 1970s.
There are misclosures and typographical (as with a typewriter) errors all over them, and one of the things I have to understand is how calcs were done in the 1970s.
Can anyone help me out on this?
I don't think math has changed much in 50 years. How you'd calculate them with a $3 calculator now is how they were doing it then, only with books in place of calculators.
Kris Morgan, post: 424791, member: 29 wrote: I don't think math has changed much in 50 years. How you'd calculate them with a $3 calculator now is how they were doing it then, only with books in place of calculators.
I find trying to find and use the offset lines and tangents to be the best means to replicate the plan.
Enter the perimeter. Put a circle over the corner where you leave the misclosure. Add the roads first and add the sidelines. Check the errors as you go and find the mistakes. Annotate and note the record distances when you need to change to math.
Who cares how they compd in the 70s. You don't know which technology they were using. They could have used some techniques of the 50s and 60s.
wfwenzel, post: 424753, member: 7180 wrote: I'm working on troubleshooting a 1970s bunch of CSMs and Plats of Surveys from the 1970s.
There are misclosures and typographical (as with a typewriter) errors all over them, and one of the things I have to understand is how calcs were done in the 1970s.
My office would run big boundary calcs on a timeshared IBM 701. They did that until 1980 when HP rolled out the HP-85B running COGO.
wfwenzel, post: 424753, member: 7180 wrote: I'm working on troubleshooting a 1970s bunch of CSMs and Plats of Surveys from the 1970s.
There are misclosures and typographical (as with a typewriter) errors all over them, and one of the things I have to understand is how calcs were done in the 1970s.
Can anyone help me out on this?
You are on the right track trying to identify the normal sources of error on the map. There are a lot of variables to consider in your question.
I have identified consistent problem areas on plats by Firm, Surveyor, geography, terrain, era and occasionally significant historical or financial events. This is the first filter i apply. If nothing pops out I look for low hanging fruit. The human brain is amazing and can spot problems on a reasonably 'to scale' drawing if you let it. Of course it only works on your own maps after recording (different thread).
The biggest problems i find from that era are curves. Im doing one now with a plat bisected by a railroad. The curves use radii that no railroad anywhere in the world has a use for. Same thing on the highway. Bust up a few curves to determine if the data works internally. Learn a little about the technical abilities of the plat preparer. Follow that by checking the bearing of missed closure. If it matches one line youve found the distance bust. If a line perpedicular to the misclosure line points from the midpoint directly to a particular corner that's likely where an angle bust occured. I would lean to a DMD sheet error if it was a small survey firm run by a curmudgeon.
These tricks go on and on. That's part of the value in reading older survey books. They lead you to where things were done on the ground. Good luck in your search, Tom
thebionicman, post: 424891, member: 8136 wrote: You are on the right track trying to identify the normal sources of error on the map. There are a lot of variables to consider in your question.
I have identified consistent problem areas on plats by Firm, Surveyor, geography, terrain, era and occasionally significant historical or financial events. This is the first filter i apply. If nothing pops out I look for low hanging fruit. The human brain is amazing and can spot problems on a reasonably 'to scale' drawing if you let it. Of course it only works on your own maps after recording (different thread).
The biggest problems i find from that era are curves. Im doing one now with a plat bisected by a railroad. The curves use radii that no railroad anywhere in the world has a use for. Same thing on the highway. Bust up a few curves to determine if the data works internally. Learn a little about the technical abilities of the plat preparer. Follow that by checking the bearing of missed closure. If it matches one line youve found the distance bust. If a line perpedicular to the misclosure line points from the midpoint directly to a particular corner that's likely where an angle bust occured. I would lean to a DMD sheet error if it was a small survey firm run by a curmudgeon.
These tricks go on and on. That's part of the value in reading older survey books. They lead you to where things were done on the ground. Good luck in your search, Tom
I found one on a Deed description written in the 1960s...a series of bearings and distances then running along a road, tangent, curve, tangent, etc. It is a mile long and half mile wide blob shaped thing which fits terrain in the mountains. On the first run through it misclosed by about 140'. So I looked for a line with close to the misclose bearing. Found one, misplaced decimal point. 141.8' tangent out of a curve, didn't notice it the first time through. Change it to 14.18' and it closed beautifully. I had also been to that spot on the ground and knew it was no where near 141' long which would shove the road into the creek.
Right off the bat here I will apologize for only scanning all the previous posts. But having experience in calculations during that time period I thought I might chime in...
I was brought up using COGO but we didn't call it that for a good number of years. The process was fairly simplistic: cosine of the bearing times the distance is equal to the difference in northings; sin of the bearing times the distance is equal to the difference in eastings. And you have to pay attention to the quadrant (obviously).
Although this method seems fairly rudimentary; working without an electronic calculator or even an old Monroe (literally pencil, paper and six place tables) can make it tedious. Most of the errors I remember never originated from deriving coordinates in the method above; they came from having a leg with coordinates at both ends and them attempting to derive a bearing and distance by long hand could get squirrely. The distance is the easy part (square root of the sum of the squares of the coordinate distance)...but attempting to use the six place tables to get a bearing with the cos-1 or sin-1 functions in tables was frustrating I remember.
Then there's the due south is 0å¡ Azimuth, north is 180å¡, which was UCG&GS protocol back then. How many remember that?
This is 1970, no digital calculators yet, they came out in 1972 or so.
I already found out why the angles only went to integer minutes; the tables only went that far, and to enter into the "seconds" world involved interpolation, another undesirable calculation. Not to mention that many instruments least read probably didn't go past a minute?
This was from 1970 and was along a twisting road up a steep grade, and they likely shot an old fence somehow and calc'ed it later. It was never monumented on the east side of the road, just the west side. and the lines were meant to be parallel for some way, but not the entire way.
So, how did they shoot the fence and translate the field notes into a description?
I am familiar with sine and cosine tables, having worked with them since grade school. But not sure how the field to office practices were done.
A lot of topo back then was either station and offset (cross sections), or stadia. The stadia shots would be plotted using a large compass rose under the vellum and a scale - setup to setup, much like a plane table and alidade in the field.
