After the platform
collapse, the top of each tower needed the loose cement removed
and then the top sealed. A scaffolding was built around each
tower to give access to the tower tops.
An elevator was connected to the scaffolding
to allow easy access to the tower top.
The tower 4 elevator supports showed an
appreciable tilt over the 200' extent of the structure. d.h.
griffin asked if we could use the theodolite
to measure the tilt of the supports. On 10 sep21 Felix and i
measured the elevator supports using the tm50 theodolite from
the entrance to the helipad.
The measurements
- We measured 3 points on the face of the tower
foundation base to define the azimuth angle for the
measurements.
- We did this at the start of the measurements, and then
at the end
- vectors were created as the differences between the
points, and then the cross products gave a normal
perpendicular to the tower base. All measurements were
then rotated so the y axis pointed perpendicular to
the tower base (+ away from tower0.
- There are 2 rails that guide the elevator. When facing the
tower/elevator the rightmost rail is on the west side
while the left rail is on the east side.
- The elevator was at ground level when the measurements
were made.
- We started measuring the rightmost rail from the ground up
to the top.
- the left rail was then measured from top to bottom.
Images showing the scaffolding and elevator rails.
There were low res and hi res photos taken
through the theodolite optics during the measured points. The
table below shows some of these measurements. In each
photo the crosshair shows where the measurement was taken.
photos of some of the
measurements
lowRes
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highRes
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Notes
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.jpeg
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shot of elevator descending
Crosshair shows measurement of tower base face.
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.jpeg
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rails the elevator rides on.
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.jpeg
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.jpeg
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lower right rail measurement (at
crosshair)
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.jpeg
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.jpeg
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right rail part way up
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.jpeg
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.jpeg
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right rail at top
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.jpeg
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.jpeg
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left rail at top
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.jpeg
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.jpeg
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left rail partway down
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Aligning the axis of the measurements
- z axis: vertical
- The theodolite was aligned so the z axis was vertical.
- y axis:Normal to tower base (+ away from tower).
- The points on the tower base were used to
generate a vector normal to the tower base (+ away
from tower).
- The angle of the normal vector in the theodolite coord
system was then used to rotate the data points so the
resultant y axis was normal to the tower base (+ away from
tower).
- x axis: parallel to tower base, (+ pointing west (to
the right))
- After the rotation, the x axis was flipped so the rail
on the right (looking at the tower) was + x.
- This ended up with a left handed coord system
The 0 location of the coordinate system:
- Z= 0
- I took the top of the tower base as z=0
- Y =0:
- A linear fit was done to z vs y.
- The y value at z=10' was used as y=0
- X= 0
- A linear fit was done to z vs x
- The x value at z=10'was used as x=0.
Plotting the data
The plots show the measured points
(after aligning the axis) (.ps) (.pdf)
- + are the measured points
- black is the right rail (west side)
- red is the left rail (east side)
- Top: z vs x position (units feet)
- The dashed green is the linear fit to the data.
- the rail are separated by about 6 feet (when the
elevator is not present).
- both rail tilt to the right (west) by about 1.3 feet
bottom to top
- The left most rail has a jog to the left at the top of
the elevator.
- Middle: z vs y position (units feet) + away from tower.
- the dashed green line is the linear fit to the data.
- both rail tilt away from the tower as you go up.
- the total tilt is about 3.6 feet away from tower.
- Bottom: y offset vs x offset
- The dashed lines are the linear fits z vs x,y
- i removed the x offsets at the bottom of each linear fit
so the x values would overlap
- This shows the y jog at the top of the structure more
clearly (about .2 feet).
Summary
- The elevator rails were measured with the tm50 theodolite
on 10sep21.
- The elevator is about 190'
- The y tilt away (away from the tower) is about 3.6 feet
- the x tilt (toward the west) is about 1.2 feet (for the
right rail)
- adding the values in quadrature gives an offset at
the top of the tower of about 3.8 feet).
processing: x101/survey/t4elevator/doit.pro
