The economical advantage of using symphot blocks, and pin-pointed 
symphot blocks, instead of the normal arbitrary line-photography array can 
be considerable. 
1 
1.1 
t2 
pt 
22 
2.4 
Economising on flight and navigation: 
Gapfree coverage is obtained from the automatic navigation system. 
In any Survey Organization or Flight Unit, statistical evidence is avail- 
able of the total number of unsuccessful flight hours due to defective 
navigation. A modern integrated survey navigation system can make all 
flight hours successful. 
Successful approach to the block’s starting point is guaranteed. 
The same reasoning as 1 above can be applied to the flight cost per year 
involved in searching for the proper starting point of the air survey. 
Savings in mapping effort and cartographic effort: 
Symmetrical block photography saves approximately 1/3 of the number 
of wing transfer points used in the side lap. 
Symmetrical model arrangement saves cartographic model-to-model 
fitting effort. 
Pin-pointed photography used for orthophotomapping produces the 
“one photo = one mapsheet”, or the “one model = one mapsheet” 
situation. One photo = one mapsheet” is a must for orthophoto- 
mapping. 
Pin-pointing by means of automated navigation instead of by 90% over- 
lap. In large-scale photography the 90% technique is not feasible 
because of the camera cycling time limitation. 
Saving on ground control: 
Pin-pointing for cadastral or reallotment mapping, where points are 
presignalised in the terrain, allows for signals and monuments to be 
located at air base distance instead of at 2/3 air base distance. This 
means not only very appreciable savings in cost (i.e. one-third), but also 
a factor 1.4 increase in the cadastral programme speed, which is even 
more important.