# Orientation Definitions for Land Surveyors

**orientation**—^{1} A rotation or set of rotations needed to make the axes of a rectangular Cartesian coordinate system parallel to the axes of another Similarly, a set of angles made by the axes of one such coordinate system with the axes of another. ^{2} The act of establishing the correct direction with reference to the points of the compass. A map is in orientation when the map symbols are parallel with their corresponding ground features. A plane table is in orientation when lines connecting positions on the plane table sheet are parallel with the pines connecting the corresponding ground objects. A surveyor’s transit is in orientation if the horizontal circle reads 0° when the line of collimation is parallel to the direction it had at an earlier (initial) position of the instrument, or to a standard line of reference. If the line of reference is a meridian, the circle will show azimuths referred to that meridian. A photograph is in orientation when it correctly presents the perspective view of the ground directly in front of the observer; or when the images on the photograph appear in the state direction from the point of observation as do the corresponding map symbols.

**orientation, absolute—**The scaling, leveling, and orientation to ground control (in a photogrammetric instrument) of a relatively oriented stereoscopic model or a group of models.

**orientation, bawl**—The establishment of the position of both ends of an air base with respect to a ground system of coordinates. In all, six elements ate required. These are essentially the three-dimensional coordinates of each end of the base. In practice, however, it is also convenient to express these elements in one of two alternative ways: (a) as the ground rectangular coordinates of one end of the base. and the difference between these, and the ground rectangular coordinates of the other end of the base; (b) as the ground rectangular coordinates of one end of the base the length of the base, and the two elements of direction (such as base direction and base tilt).

**orientation, exterior—**The determination (analytically or in a photogrammetric instrument) of the position of a camera and its attitude at the instant of exposure; over orientation. In stereoscopic instrument practice. exterior orientation is divided into two parts, relative and absolute orientation. See also *resection.*

**orientation, interior**—The interior perspective of a photograph at the instant of exposure; inner orientation. The elements of interior orientation are: calibrated focal length. location of the calibrated principal point, and calibrated lens distortion.

**orientation, relative—**The position and attitude of one of a pair of overlapping photographs with respect to the other photograph.

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

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