Terms starting with H

HACHURE

Any series of lines used on a map to indicate the general direction and steepness of slopes. The lines are short, heavy, and close together for steep slopes; longer, lighter, and more widely spaced for gentle slopes.

HALFTONE

A picture in which the gradations of light are obtained by the relative darkness and density of tiny dots produced by photographing the subject through a fine screen. 

HIGH WATER

Maximum height reached by a rising tide. The height may be due solely to the periodic tidal forces or it may have superimposed upon it the effects of prevailing meteorological conditions. Use of the "high tide" is discouraged.

  • High Water Line: Intersection of the land with the water surface at an elevation of high water.
  • High Water Mark: Line or mark left upon tidal flats, beach, or along shore objects indicating the elevation or the intrusion of high water. 

HYDROGRAPHY

Science that deals with the measurement and description of the physical features of the oceans, seas, lakes, rivers, and their adjoining coastal areas, with particular reference to their use for navigation.

Hydrographic Survey: Survey of water area, with particular reference to submarine relief, and any adjacent land.

HYDROLOGY

Scientific study of the waters of the Earth, especially with relation to the effects of precipitation and evaporation upon the occurrence and character of ground water.

HYPSOGRAPHY

Topography referred to the national geodetic vertical datum of 1929. The science or art of describing heights of land surfaces with reference to this datum.

HYPSOMETRY

Science or art of determining terrain relief, by any method.