Laserfiche WebLink
40 4P <br />Experience in the use of aerial phctographs in the map making field <br />has led us to believe that the types of len -ses and cameras used prior to <br />the year 1947 did not produce photographs of the accuracy required to <br />compile maps to meet the National Standard of Map Accuracy. <br />We have therefore attempted to classify the photography in the basin <br />area into categories as to their usability in the map making field. Most <br />of the stereo instruments now used in the map making industry are geared <br />to use photographs taken with a camera having a calibrated 6" lens, so <br />photographs taken with this type of lens is indicated in Red on the map <br />as being good for stereo compilation. <br />The areas shown in Green indicate photography taken since 1947 with <br />cameras having a calibrated 8-4 lens, and classified as being,F'air for <br />stereo compilation. <br />Areas shown in Brown indicate photo coverage prior to 1947 and such <br />areas are classified as being unsuitable for stereo compilation. <br />Recommend that areas in Green and Brown be reflown as needs arise <br />for topographic mapping in the areas. The flying should then be specified <br />for cameras having 6" lenses and for flight altitudes to best suit the <br />contour interval desired for each area; This would eliminate the necessity <br />for lar §e amounts of Supplemental Control Surveys required for the narrow <br />angle 84 lens coverage. The cost of this flying would be very little in <br />comparison to the extra cost of supplemental control required. <br />5. General Land Office Maps (Ref: LC in U.S. 1941, pp. 39, 95 and 99) <br />The General Land Office has prepared a set of State maps at the uniform <br />scale of 1 " =12 miles, which are useful for general information and reconnais- <br />sance studies. Copies of these maps for five States within the Basin are <br />attached — Louisiana, Missouri, Kansas, New Mexico, and Colorado. (There <br />is no GLO state map for Texas.) <br />The status of the surveys of the Bureau of Land Management are briefly <br />reported under Section H of the July 1950 Status Report on Activities and <br />Programs for Water Resources Conservation and Development in the Arkansas - <br />White and Red River Basins. <br />6. Geologic Mapping (Ref: LC in U.S. 1941, pp. �4 and 45) <br />Exhibit 6a is a report on "Geologic Mapping in the United States ", <br />dated July 1949 and prepared in May 1948, which was published in the bulletin <br />of the Geological Society of America. This report gives a brief but general <br />picture of geologic mapping throughout the United States. A more detailed <br />report, including maps of the Basin area., is contained in Section B of the <br />report on Status of Activities and Programs for Water Resources Conservation <br />and Development in the Arkansas -White and Red River Basins, dated July 1950. <br />State Geologic Maps have been published for all of the States in the <br />Basin except New Mexico and Oklahoma. A description of these maps is contain <br />in the mimeographed bulletin attached as Exhibit 6bo <br />c ®4 <br />