chain v edm

[TIB]

need a history lesson.
How did the average surveyor measure long lines (2000'+) over rough terrain in the 50's and early 60's? Would an early EDM or 300' (or 500') wire chain been more likely? When did the use of early EDM's become commonplace for most surveyors and what were they?
I remember HP3800 and K & E Autoranger (click click click) in the 70's, but what about 50's and 60's?
What is reasonable expectation of accuracy of measurements done with chaining in that era?

Also I have a brand new still in the box Lufkin 200' wire chain. I just learned that the correct term is canyon chain. I don't have a reel. I can't find a reel.
Any ideas on how to get a reel? I'd hate to leave such a cool survey item in a box and unused.
TIB

[LS 4722]

How did the average surveyor measure long lines (2000'+) over rough terrain in the 50's and early 60's?

Before my time but I would say the most common way was 1. Brush line 2. Set point 3. Slope chain with corrections (temp, sag, tension). The length of each transit station was limited by terrain more than the length of the chain being used.

Would an early EDM or 300' (or 500') wire chain been more likely?

EDM's for those eras were limited to night time use. Geodimeter I think was the tool used for the long base line measurements and you did not receive a distance measured at the time of measuring.

What is reasonable expectation of accuracy of measurements done with chaining in that era?

A good crew could probably do 1:15000 or better in hillside, usually agency employees over privates.

The 300' / 500' foot chain was called a Ribbon chain as well, about 1/8" wide.

[bruce hall]

dad in the mid sixties we would do pretty much what Paul said. Brush the line, pull the chain as hard as we could to straighten that thing out, set a nail, write down the slope distance and vertical angle. Didn't use a tension handle. The tapes weren't canyon tapes either. Just a regular 300 foot tape maybe an eighth to 3/16 of an inch wide.

Working for Wesley Hylen in Palm Springs in 1969 that was pretty much the same thing although the land there was pretty flat so most 300 foot pulls were done level.

Worked for Fred Crowe in Elsinore in 1970 and pretty much the same thing. No tension handles. We tried to pull the tape the same tension for each pull. We pulled it pretty hard and got a "feel" for it. We might miss the true value of the half mile by 3 or 4 tenths, maybe more, but all the chaining points were proportionate. Therefore any pipe that was set midway or quarter way on this half mile would be in the correct location.

Had a 300 foot ribbon tape. It was about a 1/16 of an inch wide. An add tape. Even used it between 1978 and 1981 before I got my first top mount. Didn't have it calibrated. Didn't know where to take it. Threw it away cleaning out the truck last month. Just taking up space.

I have a hundred foot tape and reel in the truck. It is 100.0005 feet long at 68 degrees and 25 pounds of pull. Used it twice in 25 years when I really had to know where a hundred feet was.

As a suggestion, leave the 200 footer in the box, don't buy a reel, enjoy the shooters that you have. It is so f$^*@%g nice not to have to measure around the block with a metal tape. If you take it out, you might break it, and if you do use it the guy on the other end of the tape will have to know how to use a plumb bob.

[TIB]

to traverse around the block, but just to measure or check between two points, it's handy not to have to set up the gun. But I hear ya about the guy on the other end. It's amazing how so many of todays "chainmen" have no clue how to use a chain and bob.

[Steve Martin]

An early EDM from the 1960's was the Cubic Corporation's Electrotape. It measured distances from 100m to 40 or 50km. Likely only used by large agencies due to the cost, $6,000 each, and two units were required to measure. It was very accurate even by today's standards.

While no longer in use when I started my career, I had the chance to re-adjust large geodetic networks including Electrotape measured distances to static GPS control. Generally I found centimeter or two accuracy (depending on the distance). Occasionally I found where the decimeter channel was read wrong by one or rarely two decimeters.

Background: http://amhistory.si.edu/surveying/objec ... ber=748453

http://www.cubic.com/about-us/history

[LS_8750]

I once traversed some rugged Santa Cruz Mountain terrain and hit two section corners, 120 year old record distance call, within three hundredths. I quit worring about much after that.

[RAM]

triangulation was used in open country to cover long distances. Used it in the 80's in NM due to limited range of our edm.

[E_Page]

50s & 60s were before my time as well, but I did work for a couple of outfits (MI DOT and a private company) that had not yet caught up to the use of EDMs as standard equipment by the mid 80s.

At the DOT, we used a 100' highway chain and broke chain where the terrain was too steep to measure 100' horizontally.

The private company was in west-central VA - in the Blue Ridge Mountains and nearby foothills. There, they used a 200' chain and slope chained.

The answer to what is a reasonable tolerance when comparing modern measurements to chained measurements of past eras is not a straightforward answer. A careful chaining crew could regularly achieve 1:5000 or better in moderate terrain, or about 1:3000 in rough terrain.

An alternate method of measuring distances in very rough terrain, if you could get a long line of site, say across a gully or small canyon, or from the top of a ridge to a lower meadow (or vice versa) was stadia. Realistically, the precision of a stadia reading was no better than +/- 1'. The math and trig function interpolation is another source of potential error.

However, you have to consider not what should have been done, but what commonly was done. The easier the terrain and the higher the land values, the closer "what should have been done" gets to "what was commonly done".

In rural mountain areas, it is not uncommon to find positional variance between what you actually find and what the record shows of 1 to 2 ft per 1/4 mile, and sometimes a bit worse. That's about 1:600 to 1:1300. Way below what a careful chaining crew could achieve following all of the proper procedures. But the reality was that not all procedures were carefully followed all the time, and when a traverse closure didn't come in well, it was often deemed not worth the cost and effort to remeasure questionable observations. If the site was remote and had limited access, even checking 1 or 2 courses could nearly double the field time of a survey.

When following a survey in rough terrain where the distance measurements were made by chain, and possibly some made by stadia or triangulation, the comparisons between record and measured are far less meaningful than they would be in an urban or suburban setting.

More useful, and if it exists, often more reliable as an indication of original lines are indications of use and occupation. Lacking that, use the record data to determine the center of a search area, and then to account for additional potential errors, including mistakes in the original work, work out to a distance of up to 1:50 based upon your nearest found point of the survey you're following. That is, if your nearest found point is 500' away, plan on searching up to a 10' radius; if the nearest found point is 1000' away, search up to a 20' radius.

That may seem excessive, but you may find that a course was transposed or written wrong, or that there is a significant difference between the basis of bearings used by that surveyor and the one you are on. I've had that happen as well. Found a point, traverse to the next point only to find it a seemingly excessive amount off line, but end up rotating the remaining search points and fine them all reasonably placed relative to each other.

[goodgps]

Still in practice in the 50's and 60's was the triangulation method.

This method was also used by government surveyors when they came upon rivers and other non-surveyable situations.

A line point is set out on the desired survey line at a random visible location and flagged. Another point is set at 90 degrees to said line at a place where distance could be measured to said 90 deg point. The instrument was then set on said 90 deg point and the angle was turned between the two points that are on the survey line.
right triangle calculated using 90 deg angle, the "x" degree angle and the measured perpendicular line.