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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004
like to set up a GIS or collect data using any geo-based data
collection technology.
Fist technical national regulation based on geodetic reference
systems was approved on 10^ April in 1974. It was regulating
of map and plan making in 1:2500 scales or larger. Before that
regulation large scale maps and plans were making regarding
the technical contracts of individual intuitions. Moreover, 1974
regulation was allowing land surveyors to produce maps and
plans on plane geometry. Therefore maps and plans produced
based on that regulation created problem by time. Since while
edging those maps for large areas inconsistency occurred due to
ground curvature ignorance. However at that time that was
fitting the requirements. Thereafter two technical regulations
were approved in 1976 and in 1988. The regulation in 1976
was Standard Topographic Photogrammetric Mapping in
1:5000 Scales and the regulation approved in 1988 that is also
the current regulation in Turkey was Large Scale Map
Production. After 1998 regulation maps produced in Turkey
connected to the national coordinate system, moreover maps
previously produced have been began to be converted to the
national coordinate system. Therefore today the maps based on
most GIS application have been produced regarding this
regulation. The 1988 regulation docs not allow land surveyors
to use plain geometry all maps regarding this regulation
produced based on ellipsoidal geometry and Transversal
Mercator projection. However use of this regulation is must for
only cadastral map production, nevertheless it does not regulate
all type of map production in the country. Hence maps and data
collection are still be made out of standards. In order to prevent
this and standardizing the data collection and map production
for all purposes a new regulation has been prepared and it is
currently on the stage of approval by the cabinet.
2.1 Turkish National Geodetic Network
National geodetic network establishment was begun at the
beginning of 1900 in Turkey (Ulsoy 1982, Serbetçi 1999).
National geodetic network constitutes 27 large triangulation
chain rings (~250 km x ~250 km), see Figure |.
26 28 30 x 3 x 36 40 42 m
T Y T T
tU : : eee T A m x
a AS SCHWARZES MEER d
INCF
iv
MUT
[um mA em
Y
i À. i A 1 À i À.
2 25 30 37 3l 38 38 . tc 1 46
Figure 1: National Geodetic Network
As is clearly seen on Figure 1 that the establishment of the
network was began from north-west of Turkey and moved
down to south and then again to north and south. If this order
analysed with the development process of the country it can be
seen that the geodetic networks and mapping process is very
important for national developments (Ayan et. al. 2003)
The datum of National Geodetic Network is ED50 (European
Datum 1950). This datum was realised connecting to 8
geodetic control stations of European network from Greece and
Bulgaria. More technical details of National Geodetic Network
311
can be obtained on Table 1 (Aksoy et al. 1999, Celik et al,
2003)
Table 1: Technical Specs of National Geodetic Network
Datum ED50
Ellipsoid International Hayford
Adjustment 1954
European Network Connection 8
I* Order Chain Rings | 27
Astronomic Station 99
I" & II" Order Stations 90443320
Density of I & 11" Ord. Stn. 185 km” ~(13 km/stn)
III Order Stations 255000
Density of I', II" & II'* Ord. Stn. | 13 km (3-4 km/stn)
National Network of Turkey is a hierarchical geodetic network. -
Upper order control stations always provide coordinates to
lower order control stations. While designing of the National
Geodetic Network tectonic characteristic of the country was
ignored. Scientific researches show that positions are almost 2
cm changes every year because of crustal movements. Due to
the fact National Geodetic Network deforms and distorts
(Altiner et al, 1999). In that case, result of a basic calculation
might show that from 1954 to 2004 almost 50 years past the
separation of the stations from each other achieve almost 1
metre. This figure comes out without earthquake effect. If this
is concerned the case is more dramatic. Especially after
earthquake local displacements randomly differ from the global
movements (Aliosmanoëlu 2002, Ayan et al. 2002,
Aliosmanoëlu and Çelik 2002, Celik et al. 2002). As a
summary it might be said that National Geodetic Network is not
sufficient to fit GIS, GPS, Photogrammetric and Remote
Sensing application requirements. Nevertheless it cannot be put
it away since much information has already been collected
based on this network and hence legal rights of people remain
based on this network.
There are several governmental institutions that are responsible
to take care of it and to condense it. However General
Directorate of Land Registry and Cadastre, General
Commander of Mapping are the main institutions. The others
are specifically Provincial Bank, Municipalities.
2.2 Turkish National Fundamental GPS Network
Turkish National Fundamental GPS Network (TUTGA) has
been established to remove the problem mentioned above of
National Geodetic Network, to provide reliable and robust
geodetic network infrastructure for current and future geo-based
data collection technologies, see Figure 2. TUTGA were
established between 1997 and 1999 (Anonym, 2002) and it has
been realised based on an agreement among General
Directorate of Land Registry and Cadastre and General
Commander of Mapping. It has been designed as four
dimensional (4D). Designing concept is sufficient for all type
of small scale, low resolution digital mapping and data
collection applications.
