(1) Formula.
All methods of determining percent of slope
involve the use of a formula.
The formula states that the vertical
distance, divided by the horizontal distance, times 100, equals the percent
of slope. You must be careful to always use the same unit of measurement
when using the formula.
(2) Map Method.
A large scale map may be used to approximate
the percent of slope. After the slope has been identified on the map, you
use the contour lines to determine the elevation at the bottom and top of
the slope.
The horizontal distance is determined by using the map scale.
These distances are then inserted in the percent of slope formula.
Be
careful to use the same unit of measurements. This is the least accurate of
the methods. It is helpful, however, when you have to do the route recon by
map, or when preparing for your recon. In the latter case, it helps you to
determine in advance where you may have to stop to calculate slope. This
method does not work where cuts or fills have been made to reduce the
gradient of the slope.
(3) Line of Sight and Pace. Line of sight and pace is a quick
method of estimating percent of slope. It is based on a soldier's line of
sight and pacing off to measure ground distance.
The eye level of the
average soldier is 1.75 meters (5 feet 7 inches) above the ground. The pace
of the average soldier is .75 meters (30 inches). These measurements should
be accurately determined for each member of the recon team.
With head and eyes level, a soldier stands at the bottom of
the slope. The soldier then sights a spot on the slope. This spot should
be easily identifiable. If not, another team member may be sent forward to
mark the spot. The individual making the sighting then walks forward to the
marked spot and records the number of paces.
This procedure is repeated
until the top of the slope is reached.
Fractions of an eye level height
must be estimated.
Vertical distance is then computed by multiplying the
number of eye level sightings by the eye level height. Horizontal distance
is computed by totaling the number of paces and converting it to meters,
based on the soldier's length of pace. For example, for the average soldier
it would be the number of paces times .75. These numbers are then used to
complete the formula.
g.
Road Widths.
Road widths, and how to determine them, were
discussed
on
page
1-31-1-32
in
the
section
dealing
with
route
classification. They include any constriction that reduces the traveled way
below the stated standards.
Such constrictions must be noted on the
overlay.
They include such things as narrow streets, drainage ditches,
embankments, and war damage.
The symbol for a road width constriction is
opposing triangles.
The points where the two triangles meet marks the
location of the constriction. The width of the constriction is placed at
the base of the left triangle. The length of the area that is constricted
is placed at the base of the one on the right. Both are in meters.
h.
Underpasses.
An underpass is depicted on overlays by a figure
which shows the structure's ceiling and is drawn over the route at its map
location. See Figure 1-20. The width meters is written to the left of the
symbol. The overhead clearance is written to the right of the symbol. All
measurements
MP1028
1-50
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