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Photogrammetric activity of the Italian Cadastral Survey — 5 
concerning the outer orientation of the stereoscopic pairs and the plotting of 
planimetry and contours (photogrammetric regulations). 
Finally other items specify the various verifications during the course of 
operations and the final testing. 
An accurate and extensive marking on the ground is requested for the 
limits of landed property and for all other features which otherwise would 
turn out with insufficient clearness on the photographs. The density of trian- 
gulation points as well as of the points of minor control for adjusting of photo- 
graphs in the plotting apparatus must be such that on every pair of photo- 
graphs there are at least 4 points of known co-ordinates; in practise this num- 
ber has been always surpassed, raising so the accuray of the outer orientation. 
The effective flying height is 1.800 m for scale 1:2000 and is reduced to 
1.000 m if mapping on scale 1:1000 is required, and increased to 2.500 m for 
the scale 1 : 4000. 
The final test of the map is preceded by an accurate examination of all 
records and particularly by a comparison of the map with enlargements of the 
photographs, in order to ascertain possible omissions and gross errors. Succes- 
sively the technician charged with testing. reconnaiters the ground on the hand 
of a copy of the map and assures himself of the continuity in the representa- 
tion of all topographic and cadastral features, of the exact registration of pro- 
perties, proceeding after to precise geometric controls. 
As regards testing of planimetry, the controls consist in determining — 
between well known points — by means of measurements with the Triplome- 
ter, numerous traces intersecting the limits of property and other topographic 
lines on the ground and in comparing the results with the measures deducted 
from the map. 
For testing of contours, profiles of the ground are directly surveyed by 
means of the tacheometer and the stadia, thus drawing for some zones a verti- 
cal section of the ground. The profile thus obtained is compared with the cor- 
responding one graphically desumed from the map. 
An other method is that of plotting for a second time the contour lines. 
The amount of differencies between the two plottings permits to make conclu- 
sions as to the degree of accuracy, and to establish the acceptability of the map. 
The map will be declared acceptable if such differencies overstepping 
the limits of error and ascertained in the course of final testing do not nume- 
rically exceed 1095 of the controlled points and 1596 of the partial measure- 
ments. Furthermore, as regards contours, the map will be accepted if the dif- 
ferences between the heights determined on the ground and those graphically 
desumed from the map do not exceed the limits of error by more than 10% 
of tested points. 
Maps which do not correspond to the above limitations, will not be ac- 
cepted; equally refused are sheets where 2 or more gross errors are ascertained,