With this apparatus, it is possible the marking of the corresponding points with 
an error between 5 and 9 y. 
The great precision obtainable with the method of least squares in the blocks 
adjustment makes very useful the use of the aforesaid apparatus over all those grounds 
which hardly allow the reliable location of natural particulars. 
5. — GENERAL CONSIDERATIONS ON RADIAL TRIANGULATION PROCEEDING 
Radial triangulation per strips, in spite of the technical attemps for rehabilita- 
tion has not recorded, in the quadriennium 1956-1960, that practical development it 
deserves. Practical applications are really seldom and limited to 3 or 4 countries only. 
However, the radial triangulation possibilities, which analytically can be recon- 
firmed again, are not to be unconsidered. 
On the contrary, several hundred thousands square kilometres have been carto- 
graphically surveyed, at small scale, with the proceeding of slot templet which practi- 
cally monopolize the whole application of radial triangulation proceeding per blocks. 
Not always this method is applied for cartographic purposes: sometimes it is 
simply used to obtain a photographic mosaic, checked both for generical studies and 
more often, for geological purposes. 
The control points are obtained in several ways, mostly very approximately: 
astronomical points, points obtained from other types of map, etc. 
However, the results are very good. 
Being the independent checking possible, the results obtained were suitable to 
deem the precision method sufficient for cartographie purposes at small scale 
(1: 100.000 and smaller). 
In fact, errors are included within the graphical half millimeter. 
6. - FURTHER INTERESTING INFORMATION 
We think useful, for your knowledge, to report here below some information of 
a particular character and practical interest. 
They concern the use of flights at very high altitude to obtain control points at 
lower altitude. 
The firm Leopoldo Carra of Parma (Italy), for a 45.000 hectares survey on flat 
ground at the scale 1 : 5.000 and altimetrical representation with equidistant leveling 
curves of 0,50 m, executed a first flight of 4.000 m heigh with wild R.C. 5 camera- 
photo-scale 1: 26.000 — 55 photographs total: a second flight at a lower altitude — 
1.100 m with the same camera — photo-scale 1: 6.500 — 620 photographs total. 
In each model obtainable with the 55 photographs of the first flight, there is in- 
cluded a sufficient number of points allowing an absolute orientation. 
The ground points determined with topographic operations, total 219. 
The photographs of the high flight, plotted and adjusted with the plotting instru- 
ments (A 8; model scale 1 : 15.000) allowed to obtain 1870 auxiliary points on which 
to orientate the single model of the flight at lower altitude. 
The average time required to attain the points for orientation of photographs 
taken at lower altitude 1s: 2" 50" per point. 
The absolute orientation of the 620 photographs at lower altitude, has been ob- 
tained using for planimetry the 1870 points by the high flight; for altimetry, a precise 
leveling net of 430 km, and a leveling net of 699 km. 
20 
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