Even with corners that look like this at time of shooting (or much worse)? Would the sighting error be more than the range of positions you could shoot rough concrete corners at?
Those pictures are the poster child for shooting the face of the foundation and projecting the lines to derive a corner. The face of the concrete is relatively smooth and uniform. The corners are a bit rough. The ultimate point of the exercise, after all, is to determine where the building walls are. Nobody really cares particularly about the corners, except as convenient points to draw lines between to represent the walls.?ÿ ?ÿ
Here is an example of what I'm doing. Every one of these shots is reflectorless.?ÿ
Note that I could have projected the north and east walls to form the NE corner, but did not in this case because I had no access to the yard and the corner was obscured from my vision by a heavy growth of bushes and blackberries. And the focus of the effort was the south and west walls anyway.?ÿ ?ÿ
I'm going to respectfully agree and disagree on what I bolded in your quote above in regards to my specific situation (and only my specific situation--I speak for no one else).?ÿ See attached (side note--plan has been trimmed to only highlight what I wish to speak about and to remove most of the "locational" data.?ÿ If you are the original surveyor and you feel your copyright is being stepped on, please feel free to contact me and I will remove it).?ÿ I chose this plan at random as I am working around this property.?ÿ The plan is from the mid 80's, but many plans back to the late 60's/early 70's have this info in this area.?ÿ
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We have a long tradition of declaring distances from building corners to lot lines (also from fence lines to lot lines/corners).?ÿ When assembling one's "data picture" of a lot, those measurements can be very important in one's hierarchy of evidence.?ÿ Typically, one would also purchase the surveyor's notes for additional info (ie. were the building corner measurements to the siding or the foundation, how old was the siding, how new did the siding look, etc.).?ÿ When we tie-in a building, we typically do the following:
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1. Chain the whole thing (we use a tape and/or disto).?ÿ The old way is still sometimes the best way.?ÿ If things are funky, you can set the corners ~90 and run a closure at the very worst to see where your blunder is.?ÿ On larger buildings this is not always an option.
2. Shoot all building corners reflectorlessly noting the material.
3.?ÿ If the "angle" of the reflectorless shot is around 45 or greater, we try and shoot it from another setup.?ÿ Like you stated, once you get close to this angle the shot varies far too much.
4. Shoot an audit line on the wall (ie. minimum of 2 shots) so we can project out the walls to the corners like you mention above.
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Typically, we use the reflectorless shots and chuck them and all the distances recorded into starnet.?ÿ The extended audit shots are the check.?ÿ An alternative is to use the reflectorless on a large building and use the audit extensions on those (ie. if it's too big to realistically chain).?ÿ Other checks are to do the 2 points w/ 3 measurements to the building corner (ie. 2 nails in the asphalt by the corner and tape nail to nail and nail to building x2).
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I have been trying to experiment w/ aliases from 2 different setups without much luck.?ÿ The vertical always makes things funk-a-dunk unless you shoot stuff at the same height.?ÿ I contacted Microsurvey for guidance, but they also couldn't figure out an easy way to do it without running things twice (ie. 2D and 3D).?ÿ We use GNSS & RTS for most of our stuff so it makes it a bit of pain where you have to run 2 adjustments (I'm a fan of the "one and done" approach).?ÿ We are seriously debating forgetting most of the wider angle reflectorless shots and just going back to a standard prism where we know the exact side distance, setting it up perpendicular to the gun, and shooting it with an offset.?ÿ Bit of a pain to do 1 man, but so is punching all that in Starnet.
I think that you should consider just how that 1980 surveyor determined the numbers on his map. It wasn't by raying in building corners reflectorless. If you are trying to resolve boundary based on 40 year old ties to vinyl siding .... well, don't sweat a few hundredths here and there. If you are doing it using recently tied foundation corners have close look at the corners in 350rocketmike's photos and ask just what point exactly you should rely on.
Nevertheless, I agree that it is best to get shots close to the corner- you don't want to be projecting lines many feet if it can be helped. But often it serves the needs of the job if you must.?ÿ ?ÿ?ÿ
I think that you should consider just how that 1980 surveyor determined the numbers on his map. It wasn't by raying in building corners reflectorless. If you are trying to resolve boundary based on 40 year old ties to vinyl siding .... well, don't sweat a few hundredths here and there.?ÿ
Ai, thus the agree part of my statement 😉
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I'm more concerned about people checking their work against MY work down the road who will think, well, he's from the era of reflectorless total stations, GNSS, and laser scanners (ie. the part where I disagree).?ÿ I don't have the excuse that the T2 lens was scratched, the chain was dirty, the 3rd guy pulled to the wrong pin, and part of the chief's notes doubled-as toilet paper that day.
