A datum is a type of a reference from which various measurements are made. In the fields of geodesy and surveying the word datum means the point on the surface of the earth against which the position of measurements are made, they are related to the shape of the earth which is useful for computing positions.
The types of Datum's that are horizontal are used to point on the surface of the earth. The Datum's that are used to measure the underwater depths and elevations are known as vertical datum's.
There is also a type of a datum which is known as the engineering datum; in this the datum is considered as the reference point of the axis or the surface of an object.
The types of Datum's that are horizontal are used to point on the surface of the earth. The Datum's that are used to measure the underwater depths and elevations are known as vertical datum's.
There is also a type of a datum which is known as the engineering datum; in this the datum is considered as the reference point of the axis or the surface of an object.