proportioning between points

Look in the BLM Manual.

Do you care to be more specific?

Are you referring to a particular system addressed in the BLM manual? Do you apply their methodology for meander corners when proportioning in metes-and-bounds angle points? Or perhaps there is another part of the manual I have missed on this particular question.

Use the Broken Boundary or Grant Boundary adjustment, whichever one fits the situation.

You might try the ALIGN command in ACAD/Carlson.

It sort of does MOVE ROTATE and SCALE all at once.

Nate

I was taught to never change the angular relationship between the record courses for the portions of the boundary being "fit" to the found and accepted monuments, unless there was a compelling reason to do so (bust in the deed/map that could be isolated, etc...). Therefore, I would do what you suggested - rotate the record data to match the field inversed bearing between the monuments and scale appropriately. However, I always tried to do this with the entire boundary, if possible, using a "best fit" to as many of the found and accepted monuments as possible around the perimeter. This maintains the angular integrity of the closed boundary and scales the linear component up or down to match and "old chain" with a new chain. About 25 years ago I learned a very slick trick for evaluating positions between found and calculated positions by plotting out the inversed bearing and distance between each corner position (record to measured)on grid paper using a protractor and scale that quickly shows you outliers and groupings and which way to shift the record boundary points, and how much, to get a best fit to all the monuments in one iteration. Kind of hard to explain in words, but it works great.

wait for it...wait for it.....

it depends.

Proportion where appropriate, put the error where it belongs if you can nail it down.

example- recently had a retracement of r/w from the 1940-50s era- one r/w break was missing. The break was nearer the ahd found control from the bottom of what would have been VERY steep drop off a bench.+/- 250 in about that same horizontal distance-with found control along the bottom fitting well. Things on top of the bench were good also, but I was short 3+ feet in the tangent- about 1000 - between existing control- a POT on top the bench and a PC down below.

I backed in the record distance from the PC to put in the break. (editted to try to put some coherance into the post- --one should post and eat and egg sammich at the same time...)

wait for it...wait for it.....

Grant-boundary (rotate and scale), and broken-boundary (compass rule). I see that grant boundary is "similar to" rotating and scaling and broken-boundary adjustment is "similar to" the compass rule. (frankly I don't see the differences between "similar to" and "exactly like" except that maybe the blm wanted their own term for "compass rule" (aka Bowditch rule if I am not mistaken).) Crandall rule goes through a similar gyration of scaling where it preserves the angles and scales the distances in a basic "least squares" type of proportionment to the complete distance. I am not sure if it has the precise same effect if you rotate-and-scale or not. I think the crandall rule just kind of does a proportional distance using least-squares applied to the individual distances vs. the complete distance. The compass rule uses a basic proportionment of the latitudes and departures to the total summation latitudes and departures.

I am also not sure what would be the deciding factor on when to use compass rule over scalar or not. I don't think they would have a noticable difference in the field, but I guess I can experiment with that. Both methods basically are proportioning out the error. Since we aren't using any kind of weighted traverses, I don't see how some kind of weighted least squares could really apply any better factors into the analysis.

as to "wait for it...wait for it..." well, I had to have someone say it depends. Couldn't have a survey forum without that famous saying.

I favor a rotate and scale which is the same if you did a photographic enlargement/reduction of a scale drawing of the record figure to the measured distance between the end points then rotate it in. This preserves the angles and puts the error into the distances.

If the bearings and distances were the result of a compass and chain survey then the compass adjustment may be more appropriate.

The Manual reasoning seems to be that the directions are far more accurate than the distances in that it uses the rotate and scale for restoring grant boundaries.

I would recover some adjoiner field corners and add those to the mix as well.

My thoughts would be.,,, Use the proportionate method i.e. bearing and distance adjustment that best reflects the survey you are retracing. The date of the creating survey you are retracing would be important. Knowing the methods, procedures and instrumentation would dictate to me the best method of reestablishment of the lost corners, keeping in mind the most equitable distribution of error that you could support in court.

B-)
Pablo

It's appropriate to pull out the dreaded "area" call in the description. It may provide a plausible reinforcement to one mathematical theory over another, and provide that "best fit" solution. You can't ignore testing it. If you trust the measurements of the surveyor you are retracing, the area call should reflect that.

You need to free your thinking from the "Manual" and other simplistic rote solutions which tie your hands and your brain, and allow all of the facts and evidence into your analysis.

KISS, Proportioning Between Points, LSA and/or SWAG

Keep It Simple Stupid !

Given 3 distances and 2 angles between 2 points there is only one answer to proportioning the distances to meet the criteria.

There is an infinite number of solutions when one adjusts the angles, with or without adjusting the distances.

However, it is hard for those 3 lines to stand alone and what appears to be a good fit between those 2 points may have a much greater detrimental affect on the angles to and from those points through the balance of the project.

The alternative is to engage all the found evidence with all the record data in a most complicated process know as "Least Squares Analysis".

Realistically there is no middle ground, you are either In or Out.

The problem with LSA is that you have record lines and angles, but not measurements to which one can readily assign error probabilities. You thus have to have a seance and conjure up how that record was derived, ergo "Scientific Wild Ass Guess".

Paul in PA

The link below provides good verbal explanations of the various adjustments.

wait for it...wait for it.....

When prorating in the PLSS don't forget that you need to be on true north bearings. State plane bearings can really throw off the result.

And also easterly-westerly lines need to be adjusted for curvature.