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Figure 1. Photogrammetry and GPS - kinship in figuration 
c. Harmony between the photogrammetric and 
geodetic (horizontal and vertical) control. 
In classical methods, both the inner agreement 
and the "outer" harmony can be ensured by the 
national geodetic control network. Generally, 
direct measurements can not be completed between 
photo control points, therefore, the "inner 
accuracy" of the photogrammetric control will 
depend on the homogeneity of the supporting 
geodetic frame. However, the homogeneity of a 
national network in different regions is, many 
times, more than doubtful. Historical reasons 
partook in it, as well as professional - 
technical ones. The conventional partition of the 
national horizontal and vertical control nets is 
more definite! As a result, the recorded heights 
of the horizontal control points are, in general, 
definitely less accurate then their Y and X 
coordinates. For appropriate vertical control, 
photo points must be in addition, connected by 
levelling to the surrounding benchmarks. Only GPS 
is able to treat the complex problem of the 
geodetic control for photogrammetry in a global, 
three dimensional and homogeneous manner. 
5. ECONOMY AND ACCURACY 
It is impossible to give some generally valid 
formula for precise and economical computation. 
Practically every project is individual, and 
economy depends on the local circumstances and 
special conditions. Nevertheless, one can say, 
that GPS control for photogrammetry is, in almost 
every case, cheaper than any other geodetic 
method (Hajela, 1989). The larger and more 
complex a special project is, the higher saving 
is to be expected in time and money. 
In respect of accuracy, GPS - superiority is 
unquestionable. In position 3-5 ppm inner 
25 
accuracy for photo control points is usual, and 
achievable by a very customary and simple manner. 
This accuracy likely exceeds the photogrammetric 
requirements. As mentioned in paragraph 4, the 
agreement between photo control and the national 
geodetic network depends, mainly, on the accuracy 
and homogeneity of the latter. Very good results 
can be achieved, for instance, by a least square 
fitting of the adjusted and unchanged photo 
control configuration to the national horizontal 
control points. 
In height, the GPS generally is slightly less 
accurate than in position, mainly because of the 
uncertainties of the geoid undulations. However, 
connecting with precisely levelled benchmarks and 
applying an appropriate and simple estimate for 
undulations (Melzer, 1990), even in large 
photogrammetric control networks, the absolute 
height accuracy will remain in the range of 
centimeters. 
6. TWO PRACTICAL EXAMPLES 
6.1 Engineering 
In Haifa bay region, over an approximately 6X3 km 
site, 1:500 scale photogrammetric mapping was 
required for planning a new highway system. The 
accuracy standards of this engineering project 
would require carrying out an aerial 
triangulation based on 3rd order horizontal 
points. However, the special geographical 
situation and the limitation of the classical 
geodetic methods caused, historically, the total 
absence of high order control points over the 
complete planning area. Therefore, as solution, 
the whole geodetic control frame for the aerial 
triangulation (26 points in all) was measured by 
GPS based on three third order control points and 
four benchmarks (Figure 2). The average mean