Holding the two farthest points rotate your traverse figure (call them points A and B).?ÿ
-Translate entire figure to one of the points (call this point A).
-calculate the bearing or azimuth between A and B on the original survey
-rotate the traverse figure about point A so that the azimuth of A-B of your traverse matches the original survey A-B
Check the rest of the points...if they all hit within a few millimeters, you are probably as good as you will get. At that point you have to decide if you will use the record values or yours.?ÿ
Remember, with construction, the needed precision of "matching yourself" is usually an order of magnitude greater than the necessity of matching the overall control. If you stake a building, perhaps 3mm in slop in your control would be catastrophic. Use a baseline. If you are running the initial topo control 3mm is nothing.
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Establishing baselines and solid control is critical.
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@lurker?ÿ
Bonus: redundant measurements...now you get on and get a demo of Star*Net and you have something to work with!
Hi guys
Many thanks for taking the time to reply. Yes, I'm in the UK. I'm not a "licensed surveyor", but studied surveying at college and have a diploma in the subject. I've picked up so much great advice from you guys over the years
From traversing the 12-year-old stations I can see there are no huge errors, I'm only 20mm out on two stations on a site that's 190m x 60m. I think If I just go with my new station co-ordinates it will be okay. I would think the max setting out error I would get would be around 20mm. However, I'm interested in how I can get closer to the original station's co-ordinates. For sure the stations will have moved in 12 years, if my first set on station or backsight moved by 2mm this would cause the 20mm difference (between the 12-year-old station co-ordinates and the ones I got) at the other end of the site which is 190m away.
All the nails were as rusty as hell (the site is a mile from the sea), so centering on the point of the PKK nail was hard. My gut feeling is that it's a combination of centering error, station movement and the short initial backsight that has causes the poor agreement between old and new co-ordinates.
Unfortunately, I cannot see all of the stations at once to do a resection.
Best regards, Andrew
One option would be to perform a resection after setting your instrument up at least 150' away from the existing traverse stations.
Why resection and why at least 150'?
One option would be to perform a resection after setting your instrument up at least 150' away from the existing traverse stations.
Why resection and why at least 150'?
I've seen resection mentioned before as a method to spot dodgy station co-ordinates. As long as the software has enough stations to calculate a solid resection it should highlight stations that don't have a good fit to the resection.?ÿ
I'm no expert but my understanding is that in this example a resection could be performed on the original 12-year-old stations to see if any have moved or have erroneous co-ordinates. The problem with this method most of the time you'll not be able to see many of the stations from your resection station.
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Just fyi, here is a handy tip. Analyze the existing coordinates. (Discover it runs 1-300).
So, start your job out at 401. So that you have your OWN values, and coordinate names for those same points on the ground.?ÿ
Now, you can freely rotate/translate/scale your data, without entanglement with his points, and data.
Thank you,
Nate
Thanks Nate, so what you're saying is... have my own station names and co-ordinates even though they are a few mm different from the original stations?
