After the relative and absolute orientation of the models is comple-
ted, the position of the permanent points which will be used in subsequent photogra-
mmetric surveys is established. In the next step the cross sections are read, begin-
ning with the reading on the center line. Then the survey is continued from the extreme
left to the right of the center line. The operator enters manually the station number,
and then punches automatically the x, y and z co-ordinates of each significant point
along the cross section. The elevations are read twice, and an average taken for the
computations. The data are presented on a punch tape and also in typewritten form.
As the typewriter and the punch tape operate independently, any misprints can be found
by comparing these two data. If the misprint is on the tape, a correction can be pun -
ched manually. Since we employ the IBM 650 computer which requires cards, our
next step is to convert the punched tapes to punched cards.
Our first computation programs transform the x, y, and z co-ordi-
nates obtained from the A-8 into a co-ordinate system of which one axis is identical
with the center line of the railway, Fig.5. The resulting data are presented in a form
familiar to railway engineers; i. e. station numbers, distances to the left and right of
the center line, and corresponding elevations. The co-ordinates are given to 1/10 ft.
in elevation and position. The conversion of x, y, and z co-ordinates to the new
system is performed employing the following formula: -
|
d ARE HE h - C1+C> 2
It was originally planned to carry out a rigid co-ordinate transformation with the
least square adjusting. However, the results have shown that the accuracy obtained
using the above formula was sufficient for this project.
Our next program computes the vertical curves, the design quan-
tities classified according to type of material, and also slope stake data. In addition,
a second program produces punched cards for use in the Electro Dataplotter. The
graphical presentation, Fig. 7, of the data is important because it allows the design
engineer to review the photogrammetric cross sections, the slopes, and the design
cross section chosen by the electronic computer in the calculation of the earth work
quantities. As this program also computes the slope stake data and presents it in a
tabulated form, the stake-out for construction is simplified. Borrow pits are photo-
graphed and cross sections are determined in the same manner before any material
is moved.
5. DETERMINATION OF CROSS SECTION PROFILES AT DIFFERENT STAGES OF
CONSTRUCTION AND COMPUTATION OF PAY QUANTITIES
New photography is taken at different stages of construction to
obtain progress cross sections and progress quantities according to the particular
requirements of the project. In some cases, it is also necessary to obtain aerial
photography and cross sections after the overburden is removed and the bedrock
exposed, so that accurate cross sections of the rock surface can be obtained.
The final earth work quantities are computed after the grading is
completed. New photographs at a scale of 1 : 3600 are flown, they are set up in the
A -8 plotter, using the permanent ground control points located outside of the cleared
right-of-way, Fig. 8. Cross sections of the finished grade are read in the same
manner as previously and in the same location as the cross section of the ground
before construction. In this phase of the project, two basic types of programs are
used: -
(a) Progress paid quantities (borrow pits calculations) program
(b) Final pay quantities calculations program
For the progress pay quantities and borrow pit program, the calculations are essen-
tially a comparison between two surveys. The cross sections of the ground before
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