Hi all. I remember reading a post on here where someone described how once they were setup using a resection, they would re-observe all their targets again. Is somebody able to explain why this is the case? I don't typically use resections unless I have no choice, but I would like to better understand what the advantage of this is.?ÿ
edit: clicked wrong topic, apologies to NewAgeBogan
If I can be trusted to set up control, I can be trusted to resect, but the same diligence is required. That is, when resecting, take the same care as establishing control. It??s an attitude.
And always finish your setup by shooting something you laid out from control, even a nail on a batter board, for a reality check.
The resection solution will have residuals in all the measurements - including the angles. In other words, the post-solution angle to whichever of the resect control points is designated as the backsight (typically the first point sighted) will not be zero any more.?ÿ?ÿ
Some data collector softwares, such as Carlson SurvCE, store the measurements taken for resection as Note fields, so they can not be re-processed on the computer without editing. Re-shooting the points and storing them as Observation fields make it easier in the office if one wishes to re-process the collected raw data. I never take field data collector coordinate files at face value. I edit the raw data, then re-process and examine the results in the office.
After resecting when you reshoot those points you resected from it allows you evaluate the resulting position relative to what you derived it from. If the differences are small enough to make you content, you can continue on. If they are not, then you know your resection had a flaw that you need to deal with before continuing on.?ÿ
@peter-lothian Exactly. I always felt more comfortable knowing I had clean raw data to my points without any influence from the resection.?ÿ
Hi all. I remember reading a post on here where someone described how once they were setup using a resection, they would re-observe all their targets again. Is somebody able to explain why this is the case? I don't typically use resections unless I have no choice, but I would like to better understand what the advantage of this is.?ÿ
Yep. Use this a lot. Generally not something I'd do if I know that the control is robust, but can be very useful when the control is not that great (e.g., old, bad or just set with a lower accuracy instrument.?ÿ
For example:
Establish control on a site with a GNSS with an accuracy of ?ñ25mm.
Resect using GNSS control. On my instrument, this derives a least squares solution for the best fit.
Reshoot the control using the total station. This gives a revised control set that is internally much more accurate than the original GNSS control, but is also well coupled via the original GNSS control to the datums.
