AREA PRECISION

Full disclosure: I'm a 1 year+ new user of Javad (LS/T2) having transitioned from Trimble last July. The learning curve was nasty, but, the support has been great and I am basically pleased with how the system works. If my question has already been discussed somewhere on this board or I violate any other 'rules', just chalk it up to being a new kid on the block.

One of best features is the ALTA relative accuracy report. I don't do ALTA surveys, but, it is somewhat of a national standard and it is comforting to know whether or not I'm meeting it.

Something that would be equally helpful to me would be an additional feature in the area calculation routine that would give an estimated uncertainty in the computed area. (I have one commercial client for whom acreage is the most important deliverable.) There are various ways of computing or estimating this; Dr. Charles Ghilani, retired from Penn State, has published a paper (available online) on three possible methods of addressing this question. I'm using Carlson software on my office PC and I have used the Survnet menu in the past, but, it doesn't give an estimate of area precision, although it, too, has the capability of producing and ALTA report.

I think that this would be a very practical and logical addition to J-Field. Does anyone have any other suggestions?
 

Nate The Surveyor

Well-Known Member
My thoughts are that IF you factor in a theoretical error of 0.10', for every shot, however the direction of the error is random, then it zero's itself out.
If you can show more error in a particular direction, then you could get some error, but not a lot.
If you (in Carlson), could stretch a closed polylone, in various directions, you might get an idea of acreage differences,
Anyway, it sure is incredibly interesting to be surveying today. We can actually be honestly discussing this. Anyway, I'm glad to see the surveying industry advancing as it is.
I surveyed without batteries for years. Did good work too! To see how far we've come. Is incredible.
N
 
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Thanks, Nate. I'm also a pre-battery surveyor (I was going to say dinosaur) and am trying to adjust to the lack of a linear error of closure; I very rarely do a closed ground traverse circuit anymore, especially since the LS.

What I have tried is converting the LS relative error report to an Excel spreadsheet, then selecting the point combinations that represent the parcel boundary (or close to it). I then multiply the semi-major axis of the error ellipse by the length of each line to get a plus or minus area. Of course, that axis of the error ellipse may not be normal to the line between the points, so it's not going to be an accurate method, and it's not a mathematically rigorous solution like Dr. Ghilani's, but, at least it gives an estimate .

I did talk to Dean Goodman about adding this feature to Survnet; he thought that it could be done, but, he's mostly retired now and I haven't approached Carlson about it.
 
Matt: It's been some years since we discussed adding this feature to Jfield. Is it likely that this will ever happen? I know you've all been busy...
 
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