Contour line

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Coastal map of southern Alaska near the Exxon Valdez disaster . The contour lines are only mapped near the coast, while the numerical values ​​are mapped further away.

The lines of the same sea depth are referred to as depth lines in nautical charts . The depths are measured from the ship by sounding and the values ​​are referred to (“loaded”) a specific reference system ( sea ​​chart zero , e.g. LAT). Near the coast, the contours are mapped in steps of a few meters (0 - 2 - 5 - 10 meters), while in the open sea, depending on the map scale and level differences, larger equidistant distances are sufficient.

Also maps include depth contours, if on the map sheet lakes are mapped or other deep waters. The lines of the same depth do not necessarily refer to sea ​​level , but to the surface of the water. When measuring a river , the bottom of the river is usually recorded using profiles perpendicular to the direction of flow.

Less often one speaks of contour lines in a central projection . Here the term means those straight lines that run perpendicular to the panel, i.e. into the depths of the room .

See also