Maps GPS Glossary - O
oceanic survey - 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.
opisometer - An instrument that is used in order to measure straight and curved lines. It is also known as curvimeter, meilograph or map measurer.
orthographic projection - The two-dimensional graphic representation of an object formed by the perpendicular intersections of lines drawn from points on the object to a plane of projection.
orthometric height - The distance of a point above the geoid.
orthophotograph - 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.
orthophotomap - Orthophotographic map with contours and cartographic features 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 an orthophotograph.
OSGB - Ordnance Survey of Great Britain - A system similar to the U.S. UTM for Great Britain.
overedge - Any portion of a map lying outside the nominal map border (neatline).