Trying to explain traverse adjustment

that's why you charge them 2X when they ride tag along......

If he's really interested in learning about it, maybe you could pull a copy of the applicable portion of a surveying text on the subject?

I'd try something like this:

Even though this data checks out pretty well, nothing is perfect. So we accept that there are tiny amounts of error in the measurements and we don't know where. The adjustment puts the tiny errors in likely, although never perfect, places.

If we don't make the figure close mathematically, while we know it closed on the ground, then any further computations may leverage the tiny errors into larger discrepancies. Things computed from one side won't match things computed from the another side.

By doing the adjustment we make it all mathematically consistent so that we can compute anything we want from the data and know that the error won't grow beyond the tiny amounts we started with.

I will attempt a few times to explain something to a client if they ask.

After that I just say "it is a part of the procedure that I follow" and go on to the next task at hand.

Tell him that you want it as right as possible, and you have to adjust any and all error before you can begin to analyze any corner information.

Or just do like Andy and say that it is part of procedure. You could get him a DMD sheet and explain it that way.

I would carefully consider what the client is asking...

:good:

"A least squares adjustment makes everything wrong." A favorite quote of mine from another Surveyor.:-|

> ... the guy asks why I would adjust such a tight figure. I tried to explain the adjustment process ...

He asked why, not how.

>His question..."why would you move a point from the center of the dimple in your traverse nail to a new point on the edge of the dimple (0.001'+-)"?

From the mouths of babes. There really is no purpose in adjusting a 1:100,000 closure on a 1 acre boundary job, is there? That's around 0.01' you are adjusting.

There is no purpose in adjusting a 1:10,000 closure either, because that is a bust.

I would explain to the client that a by-product of an adjustment (assuming least squares) is the statistical information generated. These statistics allow me to make confidence statements about the survey (e.g., I am 99% confident the true value of this point lies within the error ellipse generated for this point). Performing an adjustment allows me to compare the quality of my work from project to project. It also helps me detect any degradation in my measuring devices or field crew. Gathering statistical results from one survey helps me plan what equipment/crew should be used for the next survey (to meet required quality standards). I would then stop and see if his eyes have gone glossy.

With that kind of closure on that short a traverse I will finish in the field wasting no time at all with closure. For the plat, add a hundreth somewhere to balance the math.

If I close 4 miles around a rural section and close typically 1:30k, I just inverse the leg furthest from my subject parcel. It puts me within a half a tenth or less on my parcel boundaries. More than good enough for any rural standard you care to swing a dead gnat at.

Closing the books - traverse adjustment

Explain to them that it is simple accounting. You have one account in the north-south and another in the east-west. North and east are credits and south and west are debits. For each shot you take, a part of it is north-south and the other part is east-west. In order for the accounts to balance out, the north and east credits should equal the south and west debits. If they don't, some adjustments have to be made and then you close the books.

I try to explain the averaging several measurements of the same line. I read a measurement from point A to point B several times and average those, and then do the same thing from point B to point A. They should be close to the same distance, and I average the two directional distances to get my distance measurement of the line.

If the client gets that, I would try to explain that on the whole traverse, you are getting your best averages on all the lines since you are returning to the same point from which you began.

I am not explaining the math exactly but trying to show the concept.

All you need to tell him is that you cant compute an area for a figure that is not closed.

How many people use 99% confidence and how many 95% or something else?

I would have never told him that I was adjusting it in the first place. You may be there all next week if you try to explain why you are rotating the bearings....

> "why would you move a point from the center of the dimple in your traverse nail to a new point on the edge of the dimple (0.001'+-)"?
>

I would have the same question. What kinda of accuracy are going for? 1:10,000' raw is fine for just about everything I do. Not trying to be a wise guy, just wondering.

> I would have the same question. What kinda of accuracy are going for? 1:10,000' raw is fine for just about everything I do. Not trying to be a wise guy, just wondering.

I've kinda been following the thoughts on this thread and was wondering the same thing.

Somebody above commented that the minute you adjust that survey, then all dimensions are wrong. Much better to say 'that is what I measured', than 'that is what I want it to be'.

Not much different than the HI thread with the gizmo. Who are we kidding here, other than ourselves.

just my non-critical $0.02

edit - that should have been 1:100,000' is fine. 1:10,000' is the state minimum here.