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Observations (Horizontal and vertical angels, distance and astronomical azimuth) to establish a national geodetic triangulation network for Turkey started in 1930s. Mesedag near Ankara has been selected as datum point for 1st order network. Although the network had been adjusted in 1954 (Defined as Turkish National Datum-1954) and afterwards was transformed into ED-50, to fill out sparsely developed areas of the network and to establish sites in locations that make the network more convenient for local use, densification and maintenance efforts had continued until 1970s. With these efforts, second, third and forth order networks were also established in order.
But since then, because of the crustal movements and earthquakes, there have been horizontal and vertical deformations in the network. Due to these regional distortions, the network integrity became unable to meet the scientific and practical demands. Analyses show that, the total amount of displacements between 2003 and 1944 is about 1-3 m at some parts of the network. A need for a new national geodetic network emerged and it was considered to be based on GPS technology. Therefore the new fundamental geodetic network was established through the measurements and processing studies between the years 1997 and 1999 and called Turkish National Fundamental GPS Network 1999 (TFGN-99).
904 Ist order points
1483 IInd order Ist rank points
1828 IInd order IInd rank points
95.000 IIIrd order points
350.000 IV order points