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DATUM TRANSFORMATION OF SPATIAL DATA AND APPLICATION IN CADASTRE 
A. Kisa, B. Erkek, L. Ekin 
General Directorate of Land Registry and Cadastre, Ankara, Turkey 
tk36756@tkgm.gov.tr, berkek@tkgm.gov.tr, lutfiekin@gmail.com 
Commission IV, WG IV/1 
KEY WORDS: Datum, Datum Transformation, Cadastral Maps, Data Harmonization, Cadastre Web Services, Land Registry 
ABSTRACT: 
In Turkey, cadastral works have been started with local-based works in 1924 and speeded up after 1950's by using photogrammetry. 
Different measurement methods, coordinate systems and scales have been used in these works. As a result of primary cadastral 
activities two main products are generated; cadastral maps and title deeds. After this, cadastral data live on the maps, by cadastral 
activities carried out by cadastral offices and title deed data live on the registrations by land registration activities carried out by land 
registration offices. Up to 2005 different references systems such as local (graphic) and ED50 have been used for Cadastral maps 
production. 
2000’s Land Registry and Cadastre Information System (TAKBIS) Project has started as a pilot application by Land Registry and 
Cadastre (TKGM). After completion of pilot project spreading activities started in 2005 and still has been ongoing. On the other hand 
The government has taken the decision to finish primary cadastral activities within three years. The primary cadastral activities 
completed at the end of 2008. And also TKGM has completed metadata portal in 2008. At last, cadastral map updating (renovation) 
started in 2009 by using digital orthophoto with 30 cm GSD. 
Today people have great expectations in accomplishing digital cadastral services, they need correct, reliable, easy and quick 
accessible land register and cadastral survey information. Even such request expressed in INPIRE directive by using ISO 191XX data 
standards. This means we have great hard work for spatial data conversion, datum and data transformation for map and cadastral data 
harmonization. 
This paper presents results of investigation of used cadastral maps and used datums of the TKGM and possible transformation 
methods of datum and some recommendations for future applications. 
1. INTRODUCTION 
According to ISO TC 211 and OPEN GIS standards, 
“Coordinate Conversion” includes the mathematical relations of 
coordinates between same reference coordinate systems. 
“Coordinate Transformation”, on the other hand, includes the 
relations of different reference coordinate systems. Coordinate 
transformation is named as “DATUM TRANSFORMATION” 
as well. In general, the primary concern of map users is the 
transformation between coordinates produced from the main 
reference coordinate system — ITRF “International Terrestrial 
Reference Frame” which was formed using space techniques 
and coordinates of existing networks. 
According to ISO TC 211 and OPEN GIS standards, accuracy 
as data quality is defined as Network Accuracy. Network 
accuracy or absolute accuracy is the accuracy with regard to 
datum. This accuracy can be identified only by control 
surveying. In datum transformation, “Fitting Accuracy” has also 
to be calculated as an indication of integration between data and 
model. This value is the internal accuracy “m0” and may not be 
concordant with network accuracy. 
An accurate, reliable and persistent datum transformation 
depends on the parameters below: 
1) The structure and accuracy of networks for both systems. 
Today, accurate, undistorted and homogenous position 
accuracies are obtained through GNSS technique. However, old 
networks produced by terrestrial techniques include many less 
accurate systematic effects. ITRF is managed as dynamic 
network, whereas old networks are managed in static structure. 
2) The size of transformation area affects transformation 
accuracy and method. Therefore, obtaining different 
transformation accuracies using different methods for regional 
or local areas is in the possibility. In general, required 
accuracies can be obtained through evaluating very large and 
problematic areas in pieces. In the next step, persistence can be 
provided by combining these pieces. 
3) The number of common points used in transformation and 
their distribution affects accuracy. For this reason, point density 
degree has to be as high as possible. 
4) The mathematic and stochastic model used in datum 
transformation can be chosen with respect to the three factors 
above. The most important point to take into consideration 
while choosing the model is the possible systematic effects in 
network. These effects can be enumerated as crustal 
movements, edge measures in different scales etc. Some of the 
models in literature are enumerated below: