# Position Definitions for Land Surveyors

**position****—**^{1}** **Data which define the location of a point with respect to a reference system. ^{2} The place occupied by a point on the surface of the Earth**. **^{3}The coordinates which define the location of a point on a geoid or ellipsoid. ^{4} A prescribed setting (reading) of the horizontal circle of a direction theodolite which is to be used for the observation on the initial station of a series of stations which are to be observed.

**position, apparent****—**An astronomical tern applied to the observable position of a star, planet, or the sun; the data for meridian passage, right ascension and declination of the body are tabulated in an ephemeris for periodical dates and for indicated moments of time. These data are distinguished from the mean annual position of a star; from the many influences affecting the position of a planet; and from the mean sun whose place at meridian passage differs from that of the real sun by the indicated equation of time.

**position, astronomical****—**^{1} A point on the Earth whose coordinate have been determined as a result of observations of celestial body. The expression is usually used in connection with positions on land determined with great accuracy for survey purposes. ^{2} A point on the Earth defined in terms of astronomical latitude and longitude.

**position, field****—**A position computed while field work is in progress to determine the acceptability of the observations or to provide preliminary position for other purposes.

**position, geodetic****—**A position of a point on the surface of the Flan expressed in terms of geodetic latitude and geodetic longitude. geodetic position implies an adopted geodetic datum. In a complete record of a geodetic position, the datum must be stated.

**position, geographic****—**The position of a point on the surface of the Earth expressed in terms of latitude and longitude, either geodetic astronomic.

**position, relative****—**The location of a point with respect to the locations of other points. The relative positions of *two *points whose locations expressed in the same coordinate system are given by the differences of their coordinates or by a direction and distance from one of the points to the other.

**position error—**^{1}The error of a position**. **^{2}An error of an instrument reading due to location or orientation.

**positional error** [CARTOGRAPHY]**—**The amount by which a cartographic feature fails to agree with its true position.

**positional tolerance****—**The amount of uncertainty allowed for any position on a survey; ordinarily at a 95 percent confidence interval.

**positioning, direct—**See *observation, direct.*

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Source: NSPS “Definitions of Surveying and Related Terms“, used with permission.

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