inch for 6 inch cameras. Such photography covers a
band 7200 ft. or 9000 ft. wide along the proposed
route.
c. An uncontrolled mosaic (Figure 1) is prepared from
contact prints of this photography. Alternate route
locations are indicated on this mosaic for presenta-
tion to highway boards and interested civic groups.
An approximate center line profile may be prepared Hi
from the existing maps. p
d. The same photography is used in a stereoplotter such
as the Kelsh, Nistri, Balplex, or Wild A 8 to prepare
a topographic map. The usual scale is 1 inch equals
200 ft., with a contour interval of 5 ft. One or
more "paper locations" are selected on this map.
These are analyzed in terms of property acquisition
costs, access, structures, earthwork, etc. Profiles
and cross sections deduced from the contour lines
are used for the earthwork estimates.
Step III -- Roadway Design
a. When the final paper line is approved on the map,
ties to the preliminary field control traverse are
computed. The center line is then surveyed in the |
field and signalized at 400 ft. intervals. Bench I
marks are set and the center line profile is levelled. |
b. A new set of air photos is flown over the selected
center line at scale 200 ft. per inch or 250 ft. per |
inch. This will cover a band 1800 or 2250 ft. along Hl
the center line. Wing point vertical control for fil}
the stereomodels may be established either before or
after this photography.
C. Alignment sheets are plotted at scale 1 inch equals Ii
50 feet, and cross section lines are erected per-
pendicular to the center line at 50 ft. intervals.
These alignment sheets are then set up on the stereo-
plotting machine with the new large scale photography.
Elevations are read at significant intervals along
each of the cross section lines.
rte ce M ——————
d. These data are then employed to plot cross sections,
compute earth work quantities, estimate costs, etc.,
according to standard engineering practice.
e. At bridge and interchange sites, the same large Ii
scale photography is used to plot maps at 1 inch Il
equals 50 feet with 2 ft. contour interval. These
are frequently enlarged to 1 inch equals 20 feet
6
