The hardest part was, of course, getting there. The main staircase is "pre-code" for riser and tread dimension. We traversed to the top of staircase through the lobby.
You can see how tall the risers are and here's a nice view of the treads and 180 degree turn without a landing.
Because we couldn't realistically set on the stairs to make the 180, we taped four monitoring prisms where we could see them from both above and below.
We then turned sets to the prisms from above with the robot. Then we turned them down to face the bottom of the stair and did a resection.
A detail of one of our "prism mounts".
The bottom of the stair.
The sidewalk vault.
The basement not only protruded beneath the sidewalk, but the street as well.
In order to survey the street vault, we had to "open" a door with the "twelve pound persuader".
Two by eights holding up the street.
Our only check on accuracy, was to locate a standpipe on the sidewalk and then in the sidewalk vault below. We missed by one inch.
0.08' f~n~aye :good:
That's a far cry from the WTC. What's the purpose of your survey?
Actually it's right across the street.
And we are putting utility vaults in the street and sidewalk, so the owner is ceding his portion of the basement beyond the face of building.
The reasoning is that the street is already congested with utilities and the basement space is relatively free of utilities, pre-excavated, and we would improve the streetscape anyway.
All that duct tape would make Red Green proud!
Because we couldn't realistically set on the stairs to make the 180, we taped four monitoring prisms where we could see them from both above and below.
We then turned sets to the prisms from above with the robot. Then we turned them down to face the bottom of the stair and did a resection.
That's an very interesting solution. Not the most accurate, but the best you could do, given the conditions. And your check through the plumbing is also creative.