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International Textbook Company, Published 1941. Hardcover, iv, 136 pp.; 20 cm; illustrated with black-and-white halftone photographs, line engravings and diagrams throughout, including several double-page plates and diagrams and one folding plate.
In Very Good condition, no dust jacket. Black pebble-grained cloth, blind-stamped International Library panel and International Textbook Company monogram on front cover, blind-stamped publisher's panel at foot, gilt lettering on spine bright, reading from the foot upward as in all volumes of the series. Half-inch pale stain at head of rear hinge, with mild rubbing and a few scattered pale spots to back cover. Mild edge wear. Binding tight. Green and cream marbled endpapers, blue-stained page edges. Faint dampstaining at foot of title and contents leaves. Otherwise unmarked. Volume 306 in the bound series issued by International Textbook Company, the publishing arm of the International Correspondence Schools of Scranton, Pennsylvania. ICS grew out of a mine-safety question-and-answer column run by Thomas J. Foster in the Colliery Engineer and Metal Miner and enrolled its first class of 500 miners in 1891; cumulative enrollment reached four million by 1930, making it the most successful correspondence school in American history. The bound volumes gathered the loose serial-numbered Instruction Papers into permanent form, this one comprising a single long paper, Elements of Photogrammetry (Serial 3405, Edition 1), by George D. Whitmore, credited on the title page as Chief of Surveys at the Tennessee Valley Authority, an agency then producing some of the most ambitious aerial mapping in the country. A short opening section covers terrestrial photogrammetry, the instruments, the photographic negative, locating the principal point, and the construction of a plan from perspectives, before the book turns to the air. From there it is a working manual of aerial survey as of 1941: the airplane and crew, aerial cameras single-lens and multi-lens down to the five-lens, film magazines, lens cones, register marks and the trapezoidal Maltese-cross composite print, camera lenses, view finder and camera mount, then the flying of the job itself, direction of flight, overlap, net area, flight maps, photographic weather and the photographic index. The analytical middle of the book takes up what a vertical photograph actually shows and how far it lies: relief displacement and its adjustment, the effect of hills and valleys on scale, the height of an object as obtained from a photograph, tilt displacement, then stereoscopy and the interpretation of photographs. The last half is practical: determination of scale, ratioed and rectified photographs, compilation of control plots by the principal-point traverse and radial-line methods, the making of templets, mosaics, and finally the special plotting instruments, comparators, stereocomparators, parallactic displacement, and the multiplex aero-projector with its red and blue-green filters, tracing table and the plotting of contours. Illustrations are drawn from working practice, including a five-lens composite courtesy of Fairchild Aviation Corporation and a photograph of an operator plotting contours at a multiplex table. The text is candid that maps for military purposes are sometimes built from photographs with no ground survey at all, a remark of some weight in the year it was printed. The single copyright is 1941, with no periodic-review notice or later edition date. Printed by The Haddon Craftsmen of Scranton, printer's key 93655 at foot of the copyright page; the plates are signed BB N306-3405 for the publisher's Bluebook series. Contents: Terrestrial Photogrammetry: Introduction; Utilization of Terrestrial Photographs. Aerial Photogrammetry: Uses of Vertical Photographs; Personnel and Equipment for Taking Photographs; Airplane and Crew; Aerial Cameras; Camera Lenses; View Finder and Camera Mount; Procedure for Obtaining Vertical Aerial Photographs. Characteristics of Vertical Aerial Photographs: Displacement of Images; Relief Displacement; Adjustment for Relief Displacement; Tilt Displacement; Viewing and Interpreting Aerial Photographs; Stereoscopy; Interpretation of Photographs. Practical Application of Aerial Photographs: Determination of Scales of Aerial Photographs; Ratioed Photographs; Rectification of Photographs; Compilation of Control Plots; Mosaics; Use of Special Plotting Instruments.