Terms starting with O


Survey or examination of condition in the ocean or any part of it, with reference to animal or plant life, chemical elements present, temperature gradients, etc. 


Any point that is not directly below a sensor, but off to an angle in any direction.


Comparatively flat zone of variable width that extends from the outer margin of the rather steeply sloping shoreface to the edge of the continental shelf.


Establishing correct relationship in direction with reference to points of the compass; the state of being in correct relationship in direction with reference to the points of the compass.


Point in a system of coordinates that serves as a zero point in computing the system's elements or in prescribing its use.


Photograph having the properties of an orthographic projection. It is derived from a conventional perspective photograph by simple or differential rectification so that image displacements caused by camera tilt and terrain relief are removed.


Map produced by assembling orthophotographs at a specified uniform scale in a map format.

  • Orthophotomap: Orthophotographic map with contours and cartographic treatment, presented in a standard format, and related to standard reference systems.

  • Orthophotoquad: Monocolor orthophotgraphic map presented in a standard quadrangle format and related to standard reference systems. It has no contours and little or cartographic treatment.

  • Orthophotoscope: Photomechanical device used in conjunction with a double-projection stereoplotter for producing orthophotograph. 


Orthorectified images are the most position-accurate products offered. The orthorectification process removes image distortions introduced by the collection geometry and the terrain, and resamples the imagery to a uniform ground sample distance and user-specified map projection.


CD-ROM and 8mm are the standard delivery media, other media types are available for a fee. Internet delivery using File Transfer Protocol (FTP) is planned for the future, but is not currently available.


Any portion of a map lying outside the nominal map border (neatline).


Printing or drawing on a transparent or translucent medium intended to be placed in register on a map or other graphic and which shows details not appearing or requiring special emphasis on the base material.


New material printed on a map or chart to show data of importance or special use, in addition to those data originally printed.