Hi guys
Can the legs of a traverse cross over (like in a figure of eight)?
I was taught at survey school that legs cannot cross, but I often wish you could cross them. It would be useful in some scenarios like starting a traverse and traversing through a building at ground floor level and coming back to the first station at first or second floor level.
Can the software on Trimble Access, TBC or other softwares give you a traverse accuracy figure when you've crossed your legs.
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Cheers, Andrew
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There is no reason that I can think of why a traverse could not cross over itself.
Most traverse computations are co-ordinate based and would not take account of crossing lines, the close only based on the difference between the starting and finishing co-ordinates and the total distance traversed.
If the close program involves an area calculation, then all bets are off.
Yes. I think the 'no cross' scenario is offered so the software or check method can use the total interior angle of a closed polygon = (n - 2)180?ø.
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Hi guys
Can the legs of a traverse cross over (like in a figure of eight)?
I was taught at survey school that legs cannot cross, but I often wish you could cross them. It would be useful in some scenarios like starting a traverse and traversing through a building at ground floor level and coming back to the first station at first or second floor level.
Can the software on Trimble Access, TBC or other softwares give you a traverse accuracy figure when you've crossed your legs.
?ÿ
Cheers, Andrew
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Yes. Just do it. Measurements are Measurements.
only caveat would be if you use some sort of crapware.
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PS: never let software dictate logical sound survey procedure. if the Software has a problem demand that the vendor fix it.
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I feel that it's "ok" to cross traverse lines but remember, you get your best results with 90d angles.?ÿ
As previously stated it has more to do with your total interior angles or exterior angles. n-2*180 or n+2*180.
Yes. I think the 'no cross' scenario is offered so the software or check method can use the total interior angle of a closed polygon = (n - 2)180?ø.
If the traverse crosses itself, the angles would have to carry a sign in order to check.?ÿ The area would then have both positive and negative parts and the sum may be meaningless.
If you have least squares software, then you are not limited to a traverse, and can take advantage of cross-tie shots to improve the accuracy.
Back in total station/transit/theodolite days, we would turn angles to anything we could. We would also shoot dist if we had edm.?ÿ
Now a days, we use our javad everywhere. If it's a hard place, we put it into auto store mode, so it stores shots while we get lunch,?ÿ or do recon. Sometimes I wish we had 2 rovers, on the same job.
Inside buildings... Not so much!
N
In an age where combining RTK and terrestrial measurements is so easy to do, and so powerful a method of achieving high quality data for a minimum effort, I am always disappointed to read of people engaging in the minutiae of loop closures and the compass rule adjustment. If you are not doing least squares are you also measuring with transit and tape? Are you drafting with pen & ink? Writing proposals in a typewriter? We invest $100k plus in GPS, TS, CAD, truck & equipment and we can't find $2k for StarNet?
I feel that it's "ok" to cross traverse lines but remember, you get your best results with 90d angles.?ÿ
The guideline to avoid small angles comes from the days of triangulation.?ÿ If you are measuring both angle and distance, there is no bad angle.
As others have said, there's no reason why you can't do it.?ÿ That said, in all my years of surveying, I've never seen the need to cross lines.?ÿ Sure, cross ties.?ÿ
If I'm doing a simple wooded boundary survey where GPS really isn't needed, or wouldn't work anyway, then I'm running near the perimeter, so the lines wouldn't be crossing.
I did this, once, back in the 80's and the office guy told me to never do it again!
He came up with some lame excuse; I can't remember, but it sounded good at the time, so I've avoided it ever since.
Like others have said; it probably has something to do with area, or interior angles, or some other menial excuse, that can be rectified with today's software and methods.
I hope everyone is staying safe; I know I am...
I have run a figure 8 that worked out fine. In rugged terrain and vegetation, you traverse where you can. When it so steep you can't point the scope up or down enough, it's better to go across the valley and up the other side. I don't think adjustment software uses 180*(N-2) anymore, so that's not an issue. It's done with azimuths. And Norman OK, with all due respect, Starnet isn't appropriate for every surveyor. From these posts, I get the distinct impression there is a significant learning curve. And though I have nowhere near $100K worth of equipment, my surveys are more accurate, complete and reliable than most if not all of my competition, often without any adjustment.?ÿ
I've never been a big fan of adjustments; to me, it was like peeing in a bucket of distilled water. It really helps the pee, but not so much the water...
In other words; if you want to have a good traverse, don't add pee.
Hi guys
I tend to survey a lot of?ÿ I survey of properties for Architects, some of them in city centres, where some sort of development is intended. A lot of these types of properties are nestled between other high buildings which mean you cannot do a loop traverse around the perimeter of the site. So there is a problem linking control from the front of the building to the building's yard at the back. What I do it take control from the front of the building and by traversing through the ground floor to a nail out the back. I then do the same thing at the first or second floor. If the nail at the back has the same co-ordinates on the second traverse I know I haven't ballsed things up.?ÿ
I just wondered if I could traverse back to the starting nail like you normally would.
I use GPS about 5 times a year, and then I hire it in. I know in my area it wouldn't work in city centres anyway. Least square is something I've never really found the need to use - my work is just not that big.
Thanks for your advise and help
Cheers, Andrew
***Pedant Alert***
Least Squares isn't an "adjustment"; it's a method to develop an estimate of the true value of a quantity based on a consideration of the expected errors in observations or measurements.
StarNet is not the only LS solution, indeed, and may not be for every body. Least Squares, generally, is. Too big a learning curve, you say? A very poor argument.?ÿ
Your surveys may indeed be very good and better than most, but you cannot really prove that with only loop closures as evidence. Plus, you are cutting yourself out of a wide variety of possible alternative control net strategies that don't involve looping.?ÿ ?ÿ ?ÿ
Un adjusted vs adjusted traverse:
Traverse around a section. (Approx I mile square) closure is 2 feet, and 2-1/2 minutes of angle. This computes out to be about 1:12k closure. Based on the fact that the 2' and 2'30" did not occur all at one place, I adjust in that angular closure, to bring it to no more that about 10" per angle point. And, I throw it into the short legs.
Now, I perform a 1 acre survey at the point of closure. And, I can use the sectional traverse to set the 1 acre corners.
If I used the sectional traverse, to set the 1 acre corners, I could potentially throw the 2' of error into the 1 acre survey. This is not acceptable.
So, by adjusting, I make the traverse control network more useful.
Nate
***Pedant Alert***
Least Squares isn't an "adjustment"; it's a method to develop an estimate of the true value of a quantity based on a consideration of the expected errors in observations or measurements.
I disagree. If you change your measured values to something you believe better represents the actual situation, I would call that an adjustment, whether that is by compass rule, LS, or other method.
Any worthwhile adjustment uses additional information to guide the changes. That can be expected error statistics, sum of angles in a figure, or the fact that the starting and ending of a traverse is the same point.
