John, I can assure you the control was good 16 years ago. I checked my notes after you questioned the quality of my work.
The traverse closure was 1 in 145,436 and my level loops closed flat.
This year will be my 30th year doing this type of work. When I do something it's done right.
This was a 1 day job if everything went smooth and things were as I left them.
It didn't go well.
Trees had grown up within inches of the control.
We didn't have a chainsaw.
Nearly all of the control had been disturbed.
That's surveying!
We did a resection to search for monuments. Nearly every monument we found had been disturbed to some extent, but the search positions fell near the disturbed positions.
Knowing that I would not have any help next week, we elected to get the topo work done.
I have zero problems with gathering the raw topo data prior to finalizing the control.
Now that I'm in the office, I am looking at the quality of our resection and our check into the third control point. Initially, given the limited amount of data, it didn't look too bad. However since I DO take pride in my work, I manually calculated the resection to determine if the software reports were accurate.
It doesn't look too hot and I'm not too surprised.
I suspect that I will have to return to the site and set new control, tie in as much fixed stuff as I can and get back onto that assumed coordinate system before reducing the topo.
[sarcasm]Just have to get out the rag tape and the compass and do it right. [/sarcasm]
Use the distances and back azimuths from the known points to calculate a coordinate for each observation. Minimum observation, both faces and two distances to each known point so 4 coordinates for the instrument position. Average the coordinates, see the individual differences, calculate the weighted mean coordinate and the std. deviation.
I won't be going back out to do more resections.
The solution will be to run a new control loop, with additional off-site control (with metal guard stakes).
I will then locate the old control and make careful note of the condition of the monument. If they are leaning, I will tie the tops and then swivel them and remove the monument so I can tie the base.
I will have to tie every fixed object I can find that was located during the past surveys.
All this information will be used to get back onto the old coordinate system.
Just going to turn it into a 1 1/2 day project - no big deal.
It will have to be surveyed in another 5 years so I might as well establish some control while I still have enough evidence to do so.
imaudigger, post: 372153, member: 7286 wrote: I won't be going back out to do more resections.
The solution will be to run a new control loop, with additional off-site control (with metal guard stakes).
I will then locate the old control and make careful note of the condition of the monument. If they are leaning, I will tie the tops and then swivel them and remove the monument so I can tie the base.
I will have to tie every fixed object I can find that was located during the past surveys.All this information will be used to get back onto the old coordinate system.
Just going to turn it into a 1 1/2 day project - no big deal.
It will have to be surveyed in another 5 years so I might as well establish some control while I still have enough evidence to do so.
Hate it when that happens, but that's why we check things, looks like you have it well in hand
imaudigger, post: 372153, member: 7286 wrote: The solution will be to run a new control loop, with additional off-site control (with metal guard stakes).
Great idea! I never used two point resection except when using control points I knew were good. I was aware that my instrument placement in relation to my control points was important. I commend your effort to perform the field calculations manually to check your software. Wouldn't it be nice to see the math that the programmer used?
imaudigger
I am sure the equipment you used 16 years ago was different from today.
When you go out to re-establish your control what equipment will you use this time? (just wondering)
JOHN NOLTON
John, I will use a total station like I did before, only this time, I will run trig. levels rather than using a traditional level.
imaudigger, post: 371962, member: 7286 wrote: Does anyone have a good calculation worksheet laying around in a cabinet somewhere collecting dust that they would be willing to share?
This would be for two measured distances (to known points) and single angle.
I got the same answer as you hand cranking it. However, it's a 2-point resection so, either you have to hold your angle as fixed (106å¡38'16") at the vertex, or hold the distances as fixed TO the vertex. The difference of 0.29' between call vs. found is a problem and the differences you're seeing in the computations are probably one holding the angle and one holding the distances after taking the actual distance and using law of cosines and sines to make the BB intersection and meaning the values afterward.
Since you said you tied into the third with 0.2', I think that given that data points value, you could probably find the TWO that work and dump the other one and get back closer to 0.09' from the original stuff, unless it's 0.2' in the wrong direction.
Values holding distances as measured = 4329.5927, 9489.01669
Values holding angles as measured = 4329.5366,9489.1077
I do note between my two values a split of only 0.107'. If you were to mean the two values from the two different ways, it would yield 4329.6465,9489.0621.
This would yield distances to 803 of 278.71 and to 804 of 216.97 and an angle on the ground of 106å¡40'34".
Kris Morgan, post: 372492, member: 29 wrote: I got the same answer as you hand cranking it. However, it's a 2-point resection so, either you have to hold your angle as fixed (106å¡38'16") at the vertex, or hold the distances as fixed TO the vertex. The difference of 0.29' between call vs. found is a problem and the differences you're seeing in the computations are probably one holding the angle and one holding the distances after taking the actual distance and using law of cosines and sines to make the BB intersection and meaning the values afterward.
Since you said you tied into the third with 0.2', I think that given that data points value, you could probably find the TWO that work and dump the other one and get back closer to 0.09' from the original stuff, unless it's 0.2' in the wrong direction.
Values holding distances as measured = 4329.5927, 9489.01669
Values holding angles as measured = 4329.5366,9489.1077I do note between my two values a split of only 0.107'. If you were to mean the two values from the two different ways, it would yield 4329.6465,9489.0621.
This would yield distances to 803 of 278.71 and to 804 of 216.97 and an angle on the ground of 106å¡40'34".
Kris,
He is analyzing it in a different manner.
Taking in to account ground movement and changing conditions. He decided that the original control is too disturbed to try to use as if it were semi-correct. It is good enough to find monuments but that is about it.
I like the way he is handling it. Running brand new control points and tying into as many undisturbed fixed points as possible then transforming to his original coordinate system.
Stephen Johnson, post: 372507, member: 53 wrote: Kris,
He is analyzing it in a different manner.Taking in to account ground movement and changing conditions. He decided that the original control is too disturbed to try to use as if it were semi-correct. It is good enough to find monuments but that is about it.
I like the way he is handling it. Running brand new control points and tying into as many undisturbed fixed points as possible then transforming to his original coordinate system.
I don't disagree with you or how he's handling it, I just wanted to see if I could use a $3 calculator to still solve the problem by hand without a worksheet. 🙂
Kris Morgan, post: 372559, member: 29 wrote: I don't disagree with you or how he's handling it, I just wanted to see if I could use a $3 calculator to still solve the problem by hand without a worksheet. 🙂
Hey Kris, I know this is a long shot....but do you still have Pacsoft installed and running?
I have some old T-Net files that I'd like to migrate to Autocad.
imaudigger, post: 372573, member: 7286 wrote: Hey Kris, I know this is a long shot....but do you still have Pacsoft installed and running?
I have some old T-Net files that I'd like to migrate to Autocad.
[USER=7286]@imaudigger[/USER] Sure do, and I'll do you one better. If you send me an email, I'll send you the drop box link to the program, and how to make it run on Windows 7, and the file to make it run without the dongle. Or find me on fb and send me a private message. I don't want to give my email out here.
🙂 You won't find a better deal than that today brother. 🙂
