For anyone of my generation and older you will remember this or something very similar that was a huge part of your survey up bringing.
This particular instrument was used primarily for rapping angles. We used a T1 for construction because it was lighter, a little less accurate and it was easier to zero.
There were 2 kinds of T2 that I used, one with a single and the other with a double inverted vernier.
While using the T2 for control we never zeroed up. We would just site and go. Direct, reverse, horizon, then mean it out. We would do no less than 5 sets and then if one came in with more than a 3 second split we did 5 more.
In hind site this was some accurate stuff. Would would rap the angles, remove the instrument from the tribrac (if you had your head up your ass and loosened the tribrac you started again, once the tribrac was set it stayd until the legs were moved), then toss up a distance meter, calc and adjust the parts per million and proceed to shoot several distances. I have never used an attachable distance meter.
We would do this all day doing the longer distance stuff early to beat the heat blurr, jumping from set up to set up and at times standing there waiting for the chief to set a new site. (Lot's of pace circles around those instruments loaded with cigarette butts).
The point to all of this is we did some amazingly accurate stuff in those days without the awesome money making technology of today.
Here is an example of a combo of old and new.
A few years ago I was hired to do an asbuilt on a building in old town Scottsdale. The place was 2 stories with a basement and roof that needed done so a total of 4 floors. It was gutted and all of the floors were exposed and they needed to have floor heights, footprints and column locations run to the roof.
I started with gps, I broke down the block and set 2 control points across the street on the side walk. We then leveled though the control points, adjusted the vertical and set up a freshly calibrated total station and back site on the points.
I then went to the first 2 floors and and the roof and set 2 control points on each one. I then set a tripod with a prism and freshly calibrated tribrac on each point (moving between) and had my gunner rap and shoot each point both direct and reverse 10 times, starting direct, then a flop then back to the back site each time shooting a distance. We had to traverse into the basement from the street.
After all of that I reduced and meaned everything and had my control.
Now comes the part of developing footprints and locating metal vertical columns from the first floor to the roof, the basement had concrete poured around the metal all typical in size, the footprints were pretty typical.
I started on the first floor and what did I use?? Yes that's right a T2 and a chain and we turned angles to every column and chained the distance and wrote it all down in an actual field book. In this particular instance I zeroed the gun and then turned the angles to a constant corner on each column, sometimes multiple corners. Each one was treated as an individual.
After all was said and done I had a full building footprint and column asbuilt with .03' of error from basement to roof horizontally and .02' or vertical basement to roof, all of which I meaned and developed a really cool drawing file.
Could I have been more accurate? Absolutely. However my consensus was that kind of error though 4 floors basement to roof which the only place the columns were fully exposed were the first second floors was pretty damn good. By the way there was only .005' H&V between the first and second floors.
On a side note we took level shots at each column and footprint corner using a Chicago Rod. Amazingly those floors only had a 1/4 inch +/- float in them.
This was a tedious project and I had a lot of good people working for me at the time, however I did it myself and I grabbed an old school RLS who actually taught me a lot of stuff back in the days of old out of the office went and knocked the bitch out, mostly because he knew what we doing and the idea of having to teach some newbie as I went on this project made my head want to explode.
Today it would most likely be the laser scanner for this project. I would simply set the control and then turn them loose. It would be faster. As to being accurate I am unsure because I think people are still trying figure out the whole point cloud thing. That's just my opinion.
That was the last time I used a T2. Will I ever get to use one again? Who knows. I will tell you this. It was just like riding a bike, once you do it you can't lose it.