Conformal projection : A method of projection of the surface of the earth on a plane surfce in such a way that the angle between any two lines on the earth is same as the angle between their projection on the map. Also, scale at any point in the map is same in all directions and thus maintain the fidelity of shape of figure in a map.

Control points : Stations having known position.

Contour : An imaginary line of constant elevation on the surface of ground.

Datum : A level surface taken as reference for the determination of elevations of points.

Elevation : The vertical distance of a point from a datum.

Grade or gradient : The slope of a line or rate of ascent or descent is termed as grade or gradient.

Horizontal plane : A horizontal plane is a plane which is perpendicular to the plumb line. It is also tangential to a level surface at a particular point.

Horizontal line : A line which is perpendicular to the plumb line and tangent to a level surface is a horizontal line.

Horizontal distance : In plane surveying, distance measured along a level line termed as horizontal distance.

Horizontal angle : An angle measured between two intersecting lines in a horizontal plane, is defined as a horizontal angle.

Latitude : the angular distance measured along a meridian above or below the plane of the equator.

Level surface : A level surface is the equipotential surface of the earth's gravity field. It is a curved surface and every element of which is normal to plumb line. A body of still water provides the best example of a level surface.

Level line : A line lying in a level surface is a level line. It is thus a curved line normal to the plumb at all points.

Longitude : The angular distance measured in the plane of the equator east or west of the Greenwich Meridian.

Map : Graphical representation of features on or near the surface of the earth in small scale (Example 1 : 1,00,000) on a horizontal plane and is constructed using a projection system other than orthographic.

Oblate (spheroid) : An oblate (spheroid) is a surface of revolution obtained by rotating an ellipse about its minor axis i.e., having equatorial radius greater than the polar radius.

Ovaloid : A pear shaped figure having dimension of one hemisphere larger than the other for earth, southern hemisphere is larger than the northern.

Plan : Orthographic representation of features on or near the surface of the earth in Large Scale (Example 1 : 100) on a horizontal plane.

Plumb line : The direction of the lines of force of earth's gravity field. In field surveying, it is defined by the direction of a freely suspended plumb-bob.

Reconnaissance survey : A preliminary inspection of the area to be surveyed to gather first hand information about the terrrain and the availability of infrastructurees.

Scale: A specified distance on a map representing corresponding distance on the ground.

Tri-axial ellipsoid : 3D figure having three axes of unequal dimension.

Vertical line : A vertical line is a line perpendicular to the horizontal plane.

Vertical plane : A plane containing a vertical line is vertical plane.

Vertical angle : The angle between two intersecting lines in a vertical plane, is called vertical angle.

Zenith angle : An angle between two lines in a vertical plane where one of the lines is directed towards zenith is known as zenith angle.

Zenith : A vertical line in the direction away from the centre of the earth and above the observer's head, is said to be directed to wards zenith.

Baseline : The major survey line which controls a surveying operation. It is being measured very accurately.

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