As for the precision of angle measurements between a modern MS60 and a T2, while they may both be 1" instruments they have differences in sources of non-random reading error bas on how they obtain their angle measurements.?ÿ The T2 used an angular gradient imprinted on a plate.?ÿ The plate was a possible source of non random error.?ÿ To minimize the error, you would turn multiple sets of angles, re-zero the T2 in different quadrants of the plate between sets (DBS-DFS-RFS-RBS, new quadrant and repeat).?ÿ Modern total station utilize digital incoder for reading the angles and does not have a plate per say, minimizing that possible source of error.
I understand the mechanics.?ÿ But if I'm not out of date total stations do have a plate and measure angles by means of electro-optical scanning of precise digital bar-codes etched on their rotating glass cylinders or discs, the same medium as the glass plate on a T2.?ÿ The key is the TS "spins" the plate for each pointing and reads the entire plate digitally, integrating any plate anomalies so a single pointing is essentially free from plate errors.?ÿ The T2 mimics such integration by observing multiple pointings around the plate as you say; with 8 sets I suspect plate error drops below other non random instrument errors.
Don't get me wrong, modern TSs have many features that also reduce instrument errors, automatic mislevelling corrections, trunnion axis error compensation, etc.?ÿ I'm saddened when folks poop on pop and say the T2 is less precise than modern TSs; may be (barely) true but the T2 is rugged, lightweight, uses no electricity, more waterproof and the optics are divine.?ÿ The real reason TSs including robots took over is they are much faster and can be operated by less skilled operators.
@mark-mayer There were two issues with 'flat' angles. Even after open vernier transits, most instruments would not produce accurate near zero angle measurements. That is pretty much solved. The other issue is strength of interpolated functions. Carrying around tables isn't completely a thing of the past, but we aren't slaves to them any longer.
A good exercise is to perform a strength of figure calculation using stanard formulas from old geodesy text books. It will open your eyes to the other effects of geometry. Small errors can cause big problems on near zero angle measurement. If it's too close I simply mark the intersect on line and pull over to set...?ÿ
Nah... "Freestaion, also called resection..."
Ghilani/Wolf Elementary Surveying text book describes method of resection as using angles and distances.
Carrying around tables isn't completely a thing of the past, but we aren't slaves to them any longer.
It's certainly a thing of the past with me.?ÿ (Okay, technically I carry them -- they're in the back pages of my field books -- but I haven't referred to them in decades.)
@jim-frame I have a half dozen versions I use for cadastral work. The approximations match precise compution well and help isolate probable sources of error.
done correctly, aught to work just fine
done correctly, ought to work just fine.?ÿ?ÿ
@jph I also backsight from whence I came. And usually do a stake to another point just to make sure there was no angular error.
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Thanks
A good exercise is to perform a strength of figure calculation using stanard formulas from old geodesy text books.
Could you post a figure of strength calculation?
perform a strength of figure calculation using stanard formulas from old geodesy text books. It will open your eyes to the other effects of geometry
The strength of figure I remember seeing only used angle measurements for propagating one known side.
Did you do it with all measured distances?
