surveying iii (topographic and geodetic surveys) - Modern Prepper

absolute deflections of the vertical and geoid separations for each initial point of all datums, the datumscan be joined more accurately to a single unified absolute system.PART E - GEODETIC SYSTEMS1-12. General. The amount of work and time involved in establishing a single unified absolute systemof geodetic datums is tremendous. For military purposes, we must know the distance and directionsbetween widely separated points. Therefore, we must undertake this task. In this lesson, we discussedhow geodetic datums are established and some methods by which the various datums can be connected.We also discussed the tools and techniques of geodesy. Now let's examine some of the problems.1-13. Major Datums Before World War II. Every technically advanced nation has developed its ownnational geodetic system or systems, depending on its technical, industrial, or military requirements.The systems were developed by the expansion and unification of smaller local systems or by newnationwide surveys to replace the outdated local ones. Neighboring countries normally did not use thesame geodetic datum, since the cost of establishing a separate datum was small, and the nation's militaryinterest was against the use of a common datum. International surveys on the same datum wererestricted to the measurements of long arcs across international boundaries in order to determine the sizeand shape of the earth's ellipsoid. The result of this policy was that many systems developed whichdiffered from one another remarkably, as did the map series based upon them. (An example of the manydatums in Southeast Asia is illustrated in Figure 1-22.) Due to the relatively small areas covered bythese national datums, military operations requiring geodetic information were restricted to fairly shortdistances. The development of long-range rockets and guided missiles during the war illustrated theneed for more extensive geodetic information.EN0593 1-34