SURVEYING CH 5 Flashcards
The most commonly used reference datum is
mean sea level rise
The vertical height of a point above or below a reference datum is
referred to as the
reduced level or the level of a point
are used practically in all aspects of construction:
to produce ground contours on a plan; to enable the optimum
design of road, railway or canal gradients; to facilitate ground
modeling for accurate volumetric calculations.
reduced levels of
use of reduced levels
to enable the optimum design of road, railway or canal gradients
to facilitate ground modeling for accurate volumetric calculations
is the most widely used method for obtaining the
elevations of ground points relative to a reference datum and is
usually carried out as a separate procedure from that used for
fixing planimetric position
leveling
involves the measurement of vertical distance relative to
a horizontal line of sight
leveling
is one which at all points is normal to
the direction of the force of gravity as defined by a freely
suspended plumb-bob.
level line or level surface
is one that is normal to the direction
of the force of gravity at a particular point.
horizontal line or surface
is any reference surface to which the elevations of
points are referred
datum
most common datum
msl
In order to make MSL accessible to all users throughout the
country, a series of permanent marks were established, called
bench marks
is its height above or below a reference datum.
reduced level of a point
leveling methods
- Direct or spirit leveling
- Profile leveling
- Reciprocal Leveling
- Trigonometric Leveling
- Stadia leveling
- barometric leveling
- cross-section leveling
- borrow-pit leveling
types of direct or spirit leveling
- Differential Leveling
2.Double-rodded Leveling
3.Three-wire Leveling
is the process of determining difference in
elevation of points, some distance apart by a series of set ups of a
leveling instrument along a selected route.
direct or spirit leveling
is used to determine difference in elevation between
points at designated short measured intervals along established line to
provide data from which vertical section of the ground surface can be a
curved.
profile leveling
is the process of determining the difference in
elevation between two intervisible points located at a considerable
distance apart and between points leveling could not be performed in the
usual manner.
reciprocal leveling
is using trigonometric computation in
determining difference in elevation between two points from
measurements of its horizontal or slope distance and the vertical angle
between the points.
trigonometric leveling
combines features of direct leveling with those of
trigonometric leveling.
stadia leveling
is used to determine difference in elevation
between points by measuring the variation in atmospheric pressure at each
point by means of barometer.
barometric leveling
is a representation of the ground
surface on either side of the centerline in highway construction.
cross-section leveling
is a method of determining the relative
elevations of points in borrow pit excavations for the purpose of
calculating volumes of earthworks.
borrow-pit leveling
is a process of determining the difference in elevation between
two or more points some distance apart.
differential leveling
is a fixed point of reference whose elevation is either known
or unknown
bench mark
is a reading taken on a rod held on a point of known or
assumed elevation.
backsight
is a reading taken on a rod held on a point whose elevation is to
be determined.
foresight
is horizontal distance from the center of the instrument to
the rod on which a backsight is taken.
backsight distance
is a horizontal distance from the center of the instrument to t
he rod on which a foresight is taken.
foresight distance
is an intervening point between two bench marks upon which
point foresight and backsight rod readings are taken to enable a leveling operation to continue from a new instrument position
turning point
is the elevation of the line of sight of an instrument ab
ove or below a selected reference datum.
height of instrument
is a process of determining difference in elevation along a fixed line at
designated short measured intervals such as centerline of highways or sewer.
profile leveling
is a curved line which graphically portrays the intersection of a vertical
plane with the surface of the earth.
profile
is a numerical designation given in terms of horizontal distance at any
point along a profile line
stationing
are ground rod readings which are taken along the
centerline of the proposed project to provide an accurate representation of the
ground surface.
intermediate foresights
are points which are established along a profile level route at
uniformly measured distances. These points are usually divisible by 100, 50, 30, 20, or 10.
full stations
any other intermediate points established along a profile level route
other than full stations.
plus stations
