Index map of high-altitude photography UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY Water Resources Division Washington 25, D.C. In reply refer to: June 3, 1955 Code No. 4051 0001 GROUND WATER BRANCH MEMORANDUM NO. 55.44 To: District Supervisors and Staff Scientists of Ground Water Branch From: Chief, Ground Water Branch, Washington, D.C. Subject: Index map of high-altitude photography Enclosed is a copy of the index map for the United States, showing the availability of high-altitude photography and related compilation materials. The photography is flown at altitudes between 20,000 and 32,500 feet. The resulting scale of the photographs is from 1:40,000 to 1:65,000. The material furnished by the Army Map Service is received for the Geological Survey by either the Special Maps Branch (SMB) or the Map Information Office (MIO). The high-altitude material received is (1) the film negatives, (2) the photo indices showing location of each exposure, (3) the dia-positives (the glass plates on which the photography is printed for use in the Multiplex, Kelah, or other stereo plotters), (4) stereo manuscripts (the maps prepared form the diapositives) at scale of 1:20,000 to 1:62,500, with a 200-foot contour interval.* These stereo manuscripts are constructed on the universal transverse mercator grid system and do not show geographic quadrangle maps. This high-altitude material makes it relatively inexpensive for the Special Maps Branch to supply a base map for any area for which the high-altitude photography is available. These base maps are compiled by photographing the original stereo manuscripts at the desired scale and mosaicking the resulting negatives to a UTM grid upon which a regular polyconic projection has been drawn. The joins between pieces of manuscript are checked and verified. From the mosaicked negatives, prints can be made in blue, black, or brown, on either paper, stable plastics, or metal-backed paper. Paper prints of the high-altitude photographs also may be purchased from the Topographic Division at their standard price of approximately .35 per print (lower price on large orders). In order to show the current material available, this index map will be reprinted at intervals (about every month or two). The number of copies of these future maps will be limited. Therefore, if you wish to receive the subsequent copies of this index, please make written request to this office. (s) A. N. Sayre Attachment (Map) Distribution: A, B, GS, FGO Because of the limited number of maps available, a copy is not being sent to those district offices in states where photography is neither accomplished nor planned. Copies will be furnished when photography is planned for those areas. * Information just received indicates that some manuscripts have 100 foot contours.