الفهرس 
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Abstract
In the past, the egyptain traingulation network were calculated on HELMERT -1906 and HYFORD-1910 datums directly without reduction and the geodetic maps were produced on HELMERT-1906 using mercator projection.The reduction was ignored because there were no informations about the geoid in egypt at that time.When the difference between the geoid and the ellipsoid is not small and the reduction of observations is neglected, distortions in scale and orientation may be found in the net.
The subject of this study is to lock for a best fitting datum for egypt satisfying the condition that the difference between the geiod and that ellipsoid is as minimum as possible specially when the information about the geoid are given.
The mathematical model for this study was the well known VENING MINIEZ formula under the two conditions of minimizing the two values.
Also many solutions were made by changing the number of the unknown parameters to obtain the best solution and to study the effect of these parameters on the minimization process.The result is a new datum choosen from all the solutions.This choosen new datum satisfies a best minimization for the two conditions, Also a new values for relative to that new datum were calculated.