Aerophotography and Aerosurveying

Aerophotography and Aerosurveying

Aerophotography and Aerosurveying

Aerophotography and Aerosurveying

Excerpt

There is no longer any need to preach for aerial photography--not in the United States--for so widespread has become its use and so great its value that even the farmer who plants his fields in a remote corner of the country knows its value. A progress map issued by the U.S. Department of Agriculture as of Oct. 1, 1940, indicates that aerial photography completed, in progress, or approved by that department alone extended into every state and covered approximately three-quarters of the entire continental area. Combined with areas covered by other organizations the total area that has been photographed from airplanes is over 2 million square miles. The number of photographs taken is probably not less than 3 million, and a large percentage of these have been taken during the last decade.

The pioneer work of aerophotography in the United States has been done chiefly by the Army. Aerial photographs have been employed not only to improve methods of gathering military information but also for making contoured maps and mosaics. A notable recent activity has been the making of controlled mosaics by quadrangles of areas not covered by standard maps. Although use by the Army has been extensive, it has been exceeded by that of other government organizations for making standard maps, controlling crops, conserving the soil, and making studies and plans pertaining to better utilization of land.

This book is intended for students who desire to make a systematic study of aerophotography and aerosurveying. It is the result of studies carried out through many years and an arrangement of the substance of lectures given at the Institute of Geographical Exploration of Harvard University during the last four years. The student's interest may be centered in the particular field of air work, that of extreme refinement and precision in making moderate-scale or larger scale maps of important areas under special investigation, or the more general use of aerial photographs in making exploratory or reconnaissance maps of large areas. The book is intended to give him a correct start in any of these directions.

The aim has been to hold closely to practices and methods that are fundamentally sound and have been proved in standard surveying and to exclude those which would not stand under mathematical examination. However, many approximate methods are adequate for practical purposes and hence more valuable in some respects than rigorous solu-

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