Topographic surveying; including geographic, exploratory, and military mapping, with hints on camping, emergency surgery, and photography . Fig. 93.—Projection of Photograph. The elevations of points on the terrane are determined,after the selected points have been platted in horizontal planas above, in the following manner: If the elevation of the camera station V is known, theelevation of the horizon line on the plate, inn, can be obtainedby adding the height of the instrument to the elevation of COMPUTING 304 PHOTOGRAPHIC SURVEYING. the station V. The elevations of all points on
Topographic surveying; including geographic, exploratory, and military mapping, with hints on camping, emergency surgery, and photography . Fig. 93.—Projection of Photograph. The elevations of points on the terrane are determined,after the selected points have been platted in horizontal planas above, in the following manner: If the elevation of the camera station V is known, theelevation of the horizon line on the plate, inn, can be obtainedby adding the height of the instrument to the elevation of COMPUTING 304 PHOTOGRAPHIC SURVEYING. the station V. The elevations of all points on the plates whichare bisected by the horizontal line have the same elevation asthe horizontal axis of the instrument at the station, dis-regarding curvature and refraction. The elevations of othersecondary points the plates are obtained bydetermining their elevations above or below the horizon the relations of similar triangles we have in which h is the difference of elevation between the occupiedstation and the point observed, D the horizontal distance tothe observed station A from the occupied station V, and dthe horizontal distance of the same on the picture, y beingthe ordinate of points. From the rectangular triangle VPawe find d = f s^z 00, when h= ^^^ (26) / sec &? ^ The differences of elevation taken from the perspective arepositive or negative according to the relative positions oftheir points in respect to the horizon. The computations and office platting connected withphoto
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Keywords: ., book, bookcentury1900, bookdecade1900, bookpublishernewyorkjwiley
