Notes for Civil Surveying Engineer

 Define surveying:-
Surveying is the art of determining the relative positions of points on, above or beneath the surface of the earth by means of direct or indirect measurements of distance, direction and elevation.

                                                         Fig. (a) Leveling 

Principles of Surveying:-

1. Location of a point by  measurement from two points reference.
2. Working from whole to part.

Mean Sea Level (MSL)
Average elevation of the sea surface based on hourly tide gauge measurements over a period of 19 years.

                                                Fig. (b)  Mean sea level (MSL)

Bench Mark (BM):-
A permanent reference point with a known elevation (relative to some datum, usually MSL)

Back Sight:-
It is the first reading on Bench Mark. and the firs reading when the instrument is changed.

Fore Sight:-
It is the last reading on Bench Mark. and the last reading for same line of sight before the instrument in changed.

Intermeadiate Sight:-
All the readings between B.S & F.S for the same line of sight is known as I.S.

ERRORS IN LEVELING:-
(a) instrumental

1. Error due to imperfect adjustment.
2. Error due to sluggish bubble.
3. Error due to movement of objective slide.
4. Rod not of standard length.
5. Error due to defective joint.

(b) Natural

1. Earth's curvature.
2. Atmospheric refraction.
3. Variations in temperature.
4. Settlement of tripod or turning points.
5. Wind vibrations.

(c) Personal

1. Mistakes in manipulation.
2. Mistake in rod handling.
3. Mistakes in reading the rod.
4. Errors in sighting.
5. Mistakes in recording.