English

In PHOTOGRAMMETRY, the es­tablish­ment of the POSITION of both ends of an AIR BASE with respect to a ground system of COORDINATES. In all, six elements are required. These are essen­tially the three-dimensional COORDINATES of each end of the BASE.

In PHOTOGRAMMETRY, the determining (analytically or in a photogrammetric instrument) of the POSITION of the CAMERA STATION and the attitude of the taking CAMERA at the instant of EXPOSURE. In stereoscopic instrument practice, exterior orienta­tion is divided into two parts, RELATIVE and ABSOLUTE ORIEN­TATION. Also called outer orientation.

In PHOTOGRAMMETRY, the determining (analytically or in a photogrammetric instrument) of the interior perspective of the PHOTOGRAPH as it was at the instant of EXPOSURE. Elements of interior orientation are the CALIBRATED FOCAL LENGTH, location of the calibrated PRINCIPAL POINT, and the calibrated LENS DISTORTION. Also called inner orientation.

The recreation of natural terrain features at a miniature SCALE by the optical projection of overlapping PHOTOGRAPHS. The model is formed when all corresponding LIGHT RAYS from the two PROJECTORS intersect in space. See also ORIENTA­TION: ABSOLUTE, ORIENTATION: BASAL, ORIENTATION: EX­TERIOR, ORIENTATION: INTERIOR.

In PHOTOGRAMMETRY, the determin­ing (analytically or in a photogrammetric instrument) of the POSITION and attitude of one of a pair of over­lapp­ing PHOTOGRAPHS with respect to the other PHOTOGRAPH.

Placing the PLANE TABLE in such a position that every line drawn on the SURVEY SHEET from the point which represents the POSITION of the table on the ground to any other point on the sheet, is parallel to the cor­responding line in na­ture.

Placing the in­strument in such position that 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.

Towed wire used for sweeping sea bottom when surveying SHOALS or WRECKS. It consists of a wire running from the stern of the vessel and held out on the water by an OTTER which also pulls down against a towed FLOAT. The amount of wire between FLOAT and OTTER determines the DEPTH of the outer end of the sweep. The inner end of the sweep is held to the requi­red DEPTH and in line with the stern of the vessel by a KITE.