TOPOGRAPHIC SURVEY Flashcards
A survey made to secure important
data from which a topographic map
could be made
TOPOGRAPHIC SURVEY`
Establishment of a horizontal control by measuring angular
and linear
Topographic Survey
Establishment of the vertical control by determining the
elevation control points by leveling or using plane table.
Topographic Survey
Determining the elevations and location of some important
features as many deem necessary for the preparation of
the topographic map.
Topographic Survey
Computations of elevation, distances and angles as
obtained from the previous field work undertaken
Topographic Survey
- Preparation of the Topographic map, or a representation of
terrestrial relief.
Topographic Survey
Methods of Representation of Relief
Shading
* Hachures
* Relief models
* Form lines
* Contour lines
Types of Contours
οIndex contours
οIntermediate contours
All points on any one contour have the ______ elevation.
SAME
Every contour ____ on itself, either within or beyond the limits of the map. The closure may occur within the mapped area, but often happens outside the area and hence will not appear on the map sheet.
closes
A contour which closes within the limits of the map indicates either a ________. Contours which increase in elevation represent ____; those which decrease in elevation portray ________.
summit or a depression
hills
valleys or excavations.
Contours on the ground cannot cross one another except where an ___________ is represented on a map.
overhanging cliff, a vertical ledge or
wall
Contours are __________ on a uniform slope.
spaced evenly
Contours are ________ to each other on a plane surface.
straight and parallel
_______ contours signify rough, rugged terrain.
Irregular
The horizontal distance between adjacent contours indicates the ______ of the slope of the ground. Where the contours are relatively close together, the slope is comparatively ____-; where the contours are far apart, the slope is ______.
steepness
steep
gentle
Contours cross curbs and a crowned sloping street in typical ________ curves.
U-shaped
As a contour approaches a stream, the contour turns ____ until it intersects the shore line. It then crosses the stream at right angles to the center of the bed, and turns back along the opposite bank of the stream. If the stream has an appreciable width, the contours are not drawn across the stream but are discontinued at the shore, with which
it merges.
upstream
vertical distance between two adjacent contour
lines
CONTOUR INTERVAL
SR = MD/GD
SR: scaled ratio (unitless)
MD: map distance
GD: ground distance
____ = π
πππππππππ ππ πππ
ππ ππππππππ/
ππππππ ππ ππππππππ
πͺπ°
ANALYTICAL METHOD
Hsubm/de = H/DE
Two major classifications of obtaining contours
Direct method
Indirect method
contours to be plotted are actually
traced out in the field.
Direct method
points located as regards position
and elevation are not necessarily situated on the contours to be shown, but serve, on being plotted, as a basis for the interpolation of the required contours.
Indirect method:
STEPS IN COORDINATE METHOD
- On a grid system, lay out the area by establishing corner and perimeter stakes.
- At the intersections of the grid lines, determine the elevations.
- Plot the points of known elevation to the desired scale in plan.
- Draw the contour lines by interpolation
Methods of expressing slopes
percent/ grade
degrees
grads
gradient
mils
