it is the set of constant contour lines describing the planimetrical course of the terrain They are generally obtained through manual interpolation or automatically starting from a TIN, a DEM or a DTM
Line on a map connecting points with equal elevation The difference in value between two adjacent contour lines is known as the contour interval Often the word contour is used when describing isolines
A line connecting points, on a land surface or sea bottom, which have equal elevation It is called an isobath when connecting points of equal depth below a datum