Surveying (Part-4) (General Engineering) (SSC JE)

A total station is a combination of an electronic theodolite and electronic distance measuring device (EDM).
Uses:
1. Horizontal and vertical angular measurement
2. Distance between any two points
3. Co-ordinals of observed points etc.

• Survey of India is the state agency is India that prepares maps.
CPWD– The central public works department in the Indian government authority in charge of public sector works.

• The Bureau of Indian standard is the national standards body of India under department of consumer affairs, ministry of consumer affairs, food and public distribution, Government of India.

Ranging is a process of establishing intermediate points on a straight line between two end points.

Method of ranging is two types–
(i) Direct ranging–It is done when the intermediate points are intervisible. These type of ranging done by eye, line ranger or a theodolite.
(ii) Indirect ranging or reciprocal ranging–When the two points are not intervisible or the two points are at a long distance.

Bowditch's Rule–By this rule, the total error in latitude or departure is distributed in proportion to the lengths of the traverse legs.
• Correction to latitude of any line
= (length of that line / perimeter of the traverse) × total error in latitude

Angle of elevation is the angle between horizontal line of sight and the line of sight upto an object. In case of tree angle of elevation is measured by theodolite or a clinometer.

Angle of depression–It is a angle between the horizontal line of sight and the line of sight down to an object.

Scale designations–This standard recognizes six different scales, designated as A, B, C, D, E and F and marked with 12 different scales of reduction as given below–

Characteristics of contours–
• Contour lines of different elevation can unite to form one line only in the case of a vertical cliff.
• Two contour lines having the same elevation cannot unite and continue as one line. Similarly, a single contour cannot split into two lines.
• A series of straight, parallel and equally spaced contours represent a uniform surface.

Accuracy– It may be defined as the ability of an instrument to respond to a true value of a measured variable under the reference conditions. It refers to how clearly the measured value agrees with the true value. The accuracy of an instrument can be specified in the following ways-
1. Accuracy as a "percentage of full scale reading"
2. Accuracy as a "percentage of true value"|
3. Accuracy as a "percentage of span"