Leveling in Surveying

Leveling and Contouring

• In leveling, if the back sight reading at point A is greater than the fore sight reading at point B, then B is higher than A.
• When a level is in adjustment, the line of sight of the instrument is perpendicular to the vertical axis of the instrument and parallel to the bubble tube axis.
• The height of instrument method of reducing levels is preferred when there are large numbers of intermediate sights.
• Balancing of sights means making the distance of fore sight station equal to that of the back sight station from the instrument station.

Contouring

• Closed contours of decreasing values towards their center represent a depression.
• An imaginary line joining the points of equal elevation on the surface of the earth represents a contour line.
• For true difference in elevations between two points A and B, the level must be set up at the exact midpoint of A and B.
• Contour interval is the vertical distance between two consecutive contours.

Contour Gradient and Slope

• Contour gradient is a line lying throughout on the surface of the ground and preserving a constant inclination to the horizontal.
• Contour gradient cannot be located using a level.
• If the inclination of contour gradient is given, its direction from a point may be easily located either on the map or on the ground.
• To locate the contour gradient, the level is not set at the contour gradient itself.

Curve and Bearing

• A circular curve is most suited for connecting two straights in a horizontal plane.
• The latitude of a line is negative in the south direction.
• The horizontal angle between the true meridian and magnetic meridian is known as magnetic declination.

Test your knowledge of leveling principles and techniques in surveying, including instrument setup and reading comprehension.