42 
Nevertheless, if the Centre deems it advisable the triangulation can be carried 
out twice, in such a way that each model is triangulated once with base inside 
and once with base outside. 
The second triangulation of the strip must also be executed in the direction of 
increasing X, like the first one. 
The photo which in the first test was placed on the left plate holder of the res- 
titution instrument, goes to the right plate holder; it is then sufficient to change 
the sign of the base and the orientation of the photographs can be kept. 
After the observations, one single model, the test pair, shall be orientated with 
base inside and base outside, by repeating the observations of the signalized points. 
During the sessions of the Comité Directeur and of the Commission, the minimum 
number of the models to be bridged in the triangulation tests on large scales has 
been the object of discussions. 
First the opinion prevailed not to fix the number of models to be bridged and it 
was thought to leave the Centres the greatest possible liberty for the determin- 
ation of the length cf the bridgings. 
However, before sending final instructions the responsible organs of the OEEPE 
have considered it right to fix the number of the models to be bridged at a mini- 
mum of twelve. 
ENGAGEMENTS OF THE CENTRES AND BEGINNING OF THE 
TRIANGULATIONS. 
The engagements of the different countries for the execution of the triangulations on 
large scales on strips of the polygon Alstatten - Hohenems have already been published 
by the 
As 
Secretary-General of the OEEPE. 1) 
you will know these materials are in use at the following Centres: 
For the 1st group: 
Austria 
— Bundesamt für Eich- und Vermessungswesen in VIENNA. 
Responsible Mr. BERNHARDT. 
Instrument: Wild AT. 
The Netherlands — International Training Centre for Aerial Survey — DELFT. 
Responsible Mr. VISSER. 
Instrument: Wild AT. 
Switzerland — Institut de Photogrammétrie de l'Ecole Polytechnique Fédérale 
ZÜRICH. 
Responsible Prof. ZELLER. 
Instrument: Wild A7. 
For the 2nd group: 
Germany — Still to be indicated. 
Italy 
The Ne 
— Ente Italiano Rilevamenti Fotogrammetrici (E.LR.A.) FIRENZE. 
Responsible Dr. MASSERANO. 
Instrument: Santoni IV. 
therlands — I.T.C. — DELFT. 
Instrument: Planigraph C8. 
Switzerland c c.s. 
1) Report on the activities of the OEEPE during the first half year of 1956 ''Photo- 
grammetria” 1954-55 No. 1.