?Scopic image is in 
m and maximum 
ctical errors are in 
| errors may reach 
ed negligible. The 
aps by the results 
nean error of 0.9 
s measured by the 
r less than ‘/5 the 
'aphe type D) the 
metric determina- 
ights of different 
refer to 1 : 50,000 
triangulation de- 
m at the scale of 
. mm (50 m). 
Ist order permit 
r of 1:10,000 of 
000 of the flying 
gatives are taken 
e a similar form, 
ision of a photo- 
ins" from whom 
e instructed and 
| of this theoret- 
intries and orga- 
he organizations 
ig data; control 
after plotting. 
r obtaining part 
es and operators 
cal ability much 
urther details of 
ote that certain 
while in other 
rorker during 7 
rganization but 
1e Swiss Federal 
| a topographer 
.1s surveyed in 
ensed surveyor. 
> personnel are 
und’ surveying. 
(361) 
Ideas on the arrangement of machines vary just as much. The French 
IGN has placed the machines in large rooms which accommodate about 18 
machines while other services use a very small number of machines in small 
rooms. In Sweden for example there are not more than two or three machines 
per shop. 
V. Rapid Surveys by Aerial Photography. 
These surveys naturally are mostly done in unmapped regions, where 
rapidity of execution does away with precision and for which there are no 
sharply defined tolerances. Belgium, Switzerland, Austria, and the Nether- 
lands reported no work of this kind worth mentioning. 
The large wooded areas in the north of Finland have been photographed 
and photo plans on a scale of 1:20,000 have been made from rectified photo- 
graphs to serve as a base for forestry maps at 1 : 50,000. 
In Canada rapid methods are used for 1:50,000 maps where the low 
value of the land does. not justify complete geodetic control but the report 
did not explain the process used. 
In U.S.A. rapid surveys are almost always made from Tri-Metrogon pho- 
tographs. The maps are, in general, compiled at 1:250,000. The scale of the 
vertical photograph is 1:40,000 and the plotting is done at 1 : 80,000. The 
available known control is used and supplemental pass points are obtained 
with a radial triangulation with metal arm templets. Contours are mapped 
when they can be drawn with an error of less than the interval, otherwise 
form lines or hachures are used. 
The German report mentions a survey in the Anartic. The photographs 
were taken with two cameras mounted obliquely in a plane perpendicular to 
the flight line. The photographs extended almost to the horizon on both sides. 
A first plot gave a scale of 1:500,000. Afterwards sketches were made of 
limited areas on 1:50,000 with the stereoplanigraph. 
Sweden mentioned only the military cartographic work of mosaics made 
to supplement existing maps. They experiment also with photo mosaics at 
1:20,000 for forestry development. Slotted templet radial triangulation is used. 
Generally contours are not drawn. 
The Italian report describes rapid work done for 1:100,000 scale maps 
using Nistri “Stereographometres” and Nistri stereoscopes with stereometers. 
With the Stereographometer, the work is done in two phases; first radial tri- 
angulation, then plotting the models. The Italian Hydrographic Service used 
this process in surveys of the coast of Somaliland. 
In France a survey at 1:500,000 of Adelie Land (Anartic Continent) was 
made with part of the Trimetrogon photographs taken by the Byrd Expedi- 
tion. A sketch at 1:50,000 was made of a very small area around “Point 
Geology”. : 
We do not do much of this work which might be considered marginal 
photogrammetry where all the processes and consideration of precision are 
below second order when they are not completely abstractions. 
VI. Statistical Information. 
Even though the questionnaire posed questions quite precise, the replies 
have been only general and somewhat incomplete and approximate.