# Orientation Definitions for Land Surveyors

orientation1 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.

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

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