الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Recently many countries give a great attension to the problem of determining heights. Since the height over large area is important to be determined accuratly, for many reasons, the gravity corrections ought to be investigated.
The gravity correction could be small, and therefore is ignored, or it is large and so should be considered. in order to know the significanty limits or gravity correstion on height, This research is done.
As long as the height of bench marks affect the gravity correction, an application of two leveling loops in Egypt have been taken.The height along the first loop exceeds 600mt, while the height of the second is as of nile delta. the first loop is korimate-zafarana- ras ghareb-fadel-korimate.
The second loop is cairo-tanta- port said- esmailia- suez- cairo.
Observations of the two loops can be found in appendices A and B.
Calculations and results of orthometric correction using either actual or theoritical gravity values and the optimum use of both are found in chapter 5.
Also in chapter 5, analysis of using trignometric leveling in traingulation network is done.
As a review in chapter one, introduction of heights is done. full explanation of earth`s gravity field can be found in chapter 2.
Chapter 3 is directed towards the different systems of heights. Accordingly cahpter4 shows the error analysis of vertical control networks.
Conclusion and recommendations are given in chapter 6.