Properly done, a zero-height resection is better than a single-backsight solution and will yield better results.
I hadn't thought of that but it makes sense.?ÿ The downside is you have to grade the point(s) separately which seems to defeat the purpose of using the TS in the first place.
For the sake of precision, if you are letting the point float every time you monitor, why introduce additional error into the adjustment? Why not eliminate the centering and measure-up errors?
There are no such errors, as it's not the same point -- it gets a new point number each monitoring event, and its position is determined by that event's resection.?ÿ I look at the adjusted coordinates to make sure they're within the expected tolerance, but otherwise don't use the point for anything.
The image below is a Star*Net screenshot zoomed in to the control point.?ÿ The N-S spread is about 0.013', E-W about 0.010'.
@thebionicman A full amen to that. I have even tested it to make sure and it's very true. The shape of a resection with newer instruments no longer matters.?ÿ ?ÿ"With modern instruments it is possible to do extremely tight work from resections with an angle near 180 degrees... The absolutes of yesteryear are fading fast.. "
That is a good bit of the story. The newer instruments and data colkection bring improved reliability as well. I still run sets of angles but haven't seen one bust in at least 5 years. Strength of figure is less of a concern as hand held computers are inherently more precise than interpolated values. All of it comes together to make measurement options endless.
Now if can just improve the ability to recognize evidence and treat it properly...
I used 3-point resections every once in a while years ago but that was because I was studying to take the exam. I remember the math would take a long time to manually do it and it would take almost a whole notebook paper to show my work.?ÿ
The trick is creating the unknown point in between the known points without creating angles too close to 0 degrees or 180 degrees.
2-point resections work as well but you will have 2 solutions.
Here are the different methods
I believed I used the Tienstra Method when learning this. It's satisfying when you get the correct answer after all that math. Check your work with Auto-CAD or a data collector. You can even enter this as a program in the HP 35s.