2. Leveling :- is the process used to determine a difference
in elevation between two points.
A Level is an instrument with a telescope that can be
leveled with a spirit bubble. The optical line of sight
forms a horizontal plane, which is at the same elevation
as the telescope crosshair. By reading a graduated rod
held vertically on a point of known elevation (Bench
Mark) a difference in elevation can be measured and a
height of instrument (H.I.) calculated by adding the
rod reading to the elevation of the bench mark. Once
the height of instrument is established, rod readings
can be taken on subsequent points and their elevations
calculated by simply subtracting the readings from the
height of instrument.
3.
4. Devices are classified leveling in terms of accuracy
into three categories:
1 - Precision: the settlement where the bubble is very
sensitive as are high magnification power and uses
this type of work and Geodetic Survey businesses that
require high precision.
2 - Precision medium: It is less accurate than the first
category and dominated the use of this type in most
engineering projects.
3 - low-precision devices: and make this kind of
hardware specifically for the purposes of settlement
approximate as in building projects Ltd. and
settlement cases within short distance.
5. Datum line ( M.S.L. ) :- Is the level (line), which are
attributed to it points levels on the surface of the Earth.
Which is the average sea level.
Reduced level ( R.L) :- Is the high point from datum line.
Benchmark (B .M ) :- Are fixed points information site and
attributed placed in different places until you start racing
them when conducting settlement .
Back sight ( B.S.) :- Is the first reading taken after placing
the device in any position so that we see the greatest
possible number of points required to find the elevation .
Fore sight (F.S) :- Is the last reading taken before the
transfer device
7. Intermediate sight ( I.S.) :- Is reading taken between the
back sight and fore sight reading .
Elevation of line of sight ( H.I) :- Is the imaginary vertical
level determined by the line of sight to the amount of
increase or decrease for sea level .
Tripod :- is a portable three-legged frame, used as a platform
for supporting the weight and maintaining the stability of
some other object (( plumb bob))
8. tripod
A level is an instrument giving horizontal line of
sight and magnifying the reading at a far away
distance. It consists of the following parts:
(i) A telescope to provide a line of sight
(ii) A level tube to make the line of sight
horizontal and
(iii) A leveling head to level the instrument
9.
10. Staff :-Is a wooden or metal ruler one side runway to meters
and centimeters. And is a ruler of solid wood 2 , 3 , 4 , 5
meters in length and usually 4 meters .
11. Leveling of the instrument is done to make the vertical
axis of the instrument truly vertical. It is achieved by
carrying out the following steps:
Step 1: The level tube is brought parallel to any two of the
foot screws, by rotating the upper part of the instrument.
Step 2: The bubble is brought to the centre of the level
tube by rotating both the foot screws either inward or
outward. (The bubble moves in the same direction as the
left thumb.)
Step 3: The level tube is then brought over the third foot
screw again by rotating the upper part of the instrument.
Step 4: The bubble is then again brought to the centre of
the level tube by rotating the third foot screw either
inward or outward.
12. Step 8: By rotating the upper part of the instrument
through 180 ° , the level tube is brought parallel to first
two foot screws in reverse order. The bubble will remain in
the centre if the instrument is in permanent adjustment.
13.
14. Method of taking readings on a ruler settlement
1 – direct leveling a back sight is taken on the rod held at
the bench mark ( A ) .
H..I = E.L.V of B.M. ( A ) + B.S.
Turning the telescope to bring into view the rod held on
point B afore sight is taken .
elev. Point B = H .I – F .S
check the work by the following equation :-
∑ B.S. - ∑ F.S. = Last R.L. – First R.L.
15. Closing the Level Loop
A level loop is closed either to another Benchmark or
back to the starting Benchmark. To check for errors in
the loop sum the Back sights (BS) and the Foresights
(FS). Calculate the difference between the BS and FS
(BSFS). Algebraically add this difference to the starting
elevation, to yield the closing elevation. This elevation
should be within accepted industry standards tolerances
of the closing Benchmark’s published elevation.
17. Azimuth:-
The azimuth of a line on the ground is its horizontal angle
measured from the meridian to the line.
In plane surveying, azimuths are generally measured from the
north.
Azimuths may have values between 0 and 360 degrees.
18. Bearings :-
The bearing states whether the angle is measured from
the north or the south and also whether the angle is
measured toward the east or west. For example, if a line
has a bearing of S 47° E, the bearing angle 47° is measured
from the south meridian eastward.
