The «Geodesy» tractate written by prominent encyclopedic scientist Abu Rayhan Mu?ammad ibn Ahmad Al-Biruni in 1018–1025, is in fact the instruction on the instruments and methodology of astronomical determinations of latitudes and longitudes of cities, measurements of distances between cities and specifying the Earth size. In the same tractate al-Biruni demonstrates the practical appliance of the described methodology to the determination of coordinates of certain localities situated now at the territories of several Middle-East and Central Asia states. For that purpose, the geodetic polygon of around 5400 km in perimeter was devised by al-Biruni with Bagdad as its starting point. Using the Nishapur city lying inside the polygon as the example, al-Biruni shows the possibility of further thickening of the geodetic network. The polygon in whole is bound to the point of Alexandria in Egypt being well-known astronomical center of the antiquity. Described in the tractate are several terms and methods that closely correspond to the modern instructions for devising the state geodetic network. The practical part of the tractate has never been investigated by the researches, and the tractate as a whole is the important source for the history of geodesy, especially in connection with the millennium jubilee of its creation.