Geometric Transformation Models (Helmert, Bursa-Wolf, 
Moledenski-Bedakes etc.), Two-parameter Polynomials, Finite 
Elements, Interpolation Methods (LSQ, Least Curvature, 
Triangulation etc.) (TKGM Turkish National Transformation 
Project Report 2008). 
2. GEODETIC INFRASTRUCTURE IN TURKEY 
After the adjustment of the National Fundamental Triangulation 
Network in 1954, the fact remains that some parts were revised, 
but there are errors in adjustment modeling related to the 
reduction of measurements; various plates move with different 
velocities because of tectonic properties in and around Turkey 
and these movements were not monitored systematically; 
because ED-50 coordinates were not renewed in accordance, 
points were displaced in different velocities and because the 
studies carried out before 1988 Regulation were in local 
coordinate systems, many engineering works including cadastre 
were done at local coordinate systems. 
Since inner accuracy or local accuracy criteria were minded in 
densification works, information about network accuracies was 
not required. Therefore, detailed examination cannot be done. 
Moreover, the networks, formed according to 1988 Regulation, 
provide inner integrity. However, problems arise in larger 
scales. First and second order points were calculated with 
respect to adjustment, whereas lower degree points were 
calculated by inter/re-section methods. 
Distortions resulting from crustal movements, landslides etc. in 
networks generated by conventional methods are an inevitable 
fact Every single point group of these networks forms a 
separate datum. Up to a recent history in Turkey, ED-50 was 
used and all geodetic networks, maps and measures were 
generated at this datum. The National Geodetic Network studies 
in question were began in 1950-1954 by the General Command 
of Mapping (HGK) and 449,215 points were established with 
the subsequent densifications done by the cooperation of the 
General Directorate of Land Registry and Cadastre (TKGM) 
and HGK. These networks have an accuracy of 10-20 ppm. 
Third and fourth order 285,000 triangulation points were 
established, measured and calculated for the purpose of 
producing 1/5,000 scaled standard topographic maps. These 
points, whose 71,000 were produced by HGK and rest 215,000 
by TKGM, are present within the archive of TKGM. The 
accuracy of the National Geodetic Network fell behind the 
accuracy that the modern technology has reached. In order to 
fulfil this need, the Turkish National Fundamental GPS 
Network (TUTGA), consisting of 594 points, was established 
between 1997-2001 by TKGM and HGK. The coordinates and 
velocities of TUTGA points were determined in ITRF. Relative 
accuracy of the network is 0.1-0.01 ppm, whereas point position 
accuracy is about 1-3 cm (TKGM Turkish National 
Transformation Project Report 2008). 
2.1 Some of the Results obtained between TUTGA and ED- 
50 
a) +3-5 m transformation match was obtained for whole Turkey 
with 3D similarity transformation between TUTGA99A and 
ED-50 using 220 points. 
b) +1.5-2 m transformation match was obtained for every single 
Zone with separate similarity transformations. 
c) Similar results were obtained through modeling latitude and 
longitude differences. 
d) For Izmir and Istanbul, transformation accuracies of +8 cm 
and +10 cm were obtained, respectively. 
According to the 82™ article of the Large Scale Map and Map 
Information Production Regulation, minimum transformation 
accuracy was taken as 49 cm. According to the 100^ article, 
transformation enhancement and update tasks were given to 
TKGM, HGK and universities. However, increasingly growing 
municipality borders, Metropolitan municipalities and 
countrywide projects like TUSAGA-Aktif require horizontal 
and vertical parameters persistent for whole area with high 
network accuracy or transformation grid data. Using this data 
has to be juristically guaranteed. For example, technical and 
juridical guarantee has to be provided for transferring 
information produced at ED-50 or ITRF derived from legal 
cadastre information without accuracy loss. This requirement 
constitutes the primary concern of datum transformation. 
All maps and coordinates produced countrywide until 2001 are 
on ED-50. There are around 283,000 map sheets on ED-50 
within the body of TKGM. Transformation into ITRF datum of 
these map sheets is an inevitable fact. However, most of these 
map sheets are not digital and errors coming from production 
(erroneous measurement, drawing, edging etc.) exist. Bringing 
these maps into digital form with digitizing and absolute 
transformation will transfer the existing errors to digital map 
and result in legal consequences. 
Transformation accuracy of ED-50 data and map sheet scale are 
desired to be concordant. Accuracy on 1/1,000 scaled map 
sheets is around 0.2-0.3 m and taking relative accuracy into 
consideration with respect to National Geodetic Networks, it is 
required to have common points at 10-30 km intervals whose 
coordinates are determined on ED-50 and ITRF. Thus, GNSS 
measurements will be required for a reasonable transformation 
at geodetic points that map sheets depend on and at produced 
details. This will be possible by loss in transformation accuracy 
(TKGM Turkish National Transformation Project Report 2008). 
3. COMMONLY USED DATUMS IN TURKEY 
3.1 European Datum 1950 (ED-50) 
All maps and coordinates produced countrywide until 2001 are 
on ED-50. There are around 283,000 map sheets on ED-50 
within the body of TKGM. 
Up to a recent history in Turkey, ED-50 was used and all 
geodetic networks, maps and measures were generated at this 
datum. The National Geodetic Network studies in question were 
began in 1950-1954 by HGK and 449,215 points were 
established with the subsequent densifications done by the 
cooperation of TKGM and HGK. These networks have an 
accuracy of 10-20 ppm. ED-50 represents International 1924 
Ellipsoid which was defined locally for Europe (TKGM Turkish 
National Transformation Project Report 2008). 
ED-50 takes International 1924 Ellipsoid (a-6378388 m; 
b=6356911.9461; f=1/297; e=0.08199188998) as reference 
ellipsoid, and Greenwich Meridian as prime meridian. In this 
system, Helmertturm point (®=52° 22" 51”.446 N; A=13° 03’ 
58".741 E; Geoid height (N) = 0 m; north-south component of 
deflection of the vertical ({)=3".36, east-west component of 
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