on smaller scales, additional determination of control points-when the 
photographs are already taken-is also used. For one stereomodel 4— 6 
points are generally determined for some of them only the height. 
For greater economy in preparing maps and plans by photo- 
grammetric methods, and to minimize field work, all photogrammetric 
institutions tend to use aerial triangulation in their ordinary work. Since 
almost the whole territory is covered by III'? order triangulation, as well 
as by precise levelling network and economically developed areas are 
also covered by IV” order triangulation, the application of aerial triangu- 
lation for smaller scale topogranhic mapping to larger areas is not taken 
into consideration. 
For smaller scale topographic mapping aerial triangulation 
is used in practice in some undeveloped areas where access is difficult and 
it is carried out in separate strips. Methods of graphical adjustment have 
so far been used. 
For large scale mapping at scales of 1:5,000 and 1 : 2,500, 
aerial triangulation is used for short distances (5—7 km) mostly in areas 
where access is difficult and in woodlands where the determination of 
control points with classical geodetic methods is expensive, and photo- 
grammetry in such areas usually presents the relief with limited accuracy. 
First order instruments Wild A-5 and A-7 and Zeiss C-8 are used for 
aerial triangulation. 
Rectification of aerial photographs and the preparation of 
controlled mosaics for the basic state map, cadastral and economic pur- 
poses is carried out at a scale of 1:2,500 to 1:10,000. In preparing the 
basic map by means of rectification a great saving is achieved by using 
pointed photographs, obtained by single exposure in places exactly fixed 
in advance. In this way the number of control points is reduced, because 
every point can be used on four adjacent photographs. In addition by 
marking the control points before taking the photograph (by white- 
washing, with special marks and in other ways) and using an aerial plate 
camera RC-7a, a scale ratio of 1:4 is achieved between the photographs 
and the controlled mosaics. Hence for a 1 : 5,000 scale map, photographs 
were taken at a scale of 1:20,000. In this way a strip of photographs 
covers the whole width of the sheet and therefore rectification is greatly 
speeded up. 
This method of work is extensively applied in practice. Its 
application in the determination of control points and rectification, is twice 
as economical as the method used up to now. 
Terrestrial photogrammetry is used only for filling up gaps 
in aerial photogrammetric mapping (shadows, steep slopes, etc), and for 
large scale mapping for technical purposes. For technical projects it is 
often necessary to make plans at large scales of 1:500 to 1: 1,000, parti- 
cularly in rough terrains where the use of classical surveying methods is 
very difficult. For such purposes terrestrial photogrammetry is succes- 
sfully used, mostly in hydrotechnical work, for the construction of power 
stations. 
The following applications of photogrammetry have been 
made in forestry: 
— For engineers of agriculture and forestry 80—100 hour 
courses were organized and various investigations and research in this 
field were made.