22 
The limits within which, according to the new decisions, the work had to be fi 
nished, though very ample, appeared afterwards too restricted for some of the parti 
cipant organizations. 
In fact, the Centre E.T.H. of Zürich and the Centre C.A.S.F. of Milano, at the end 
of 1961, communicated they could not comply with the engagements and retired from 
the Working Group adducing valid reasons of different character. 
Therefore, the Group of Study was made up only of the six following Centres: 
— Centre N.R.C., Ottawa, Canada 
— Centre I.G.N., Paris, France 
— Centre of the Ohio State University, U.S.A. 
— Centre of the University of the Illinois, U.S.A. 
— Centre I.T.C., Delft, Holland 
-— German Group of Centres, West-Germany. 
In the following paragraph we shall point out the phases of the execution of the 
work till the meeting of the Group, held in Milano, on October 1st, 1962. 
3 - MEETING OF THE CENTRES HELD IN MILANO ON 1ST OCTOBER 1962 
In order to make more synthetic and expressive the chronicle of the work executed 
by the Centres between September 1960 (London Congress time) and October 1st, 
1962 (Milano meeting date), we compiled Table n° 1. 
Only the Centres that kept the engagement till the end are mentioned in this 
table: in the first columns we summarize the initial phases of the forwarding of the 
photographic material and of the starting of the work preceding the London Congress. 
The Presidency having complete confidence in the loyal collaboration of the Cen 
tres, the dates contained in the table have been derived from the communications 
given by the Centres themselves. No control has been effected, except the indirect 
control of the periodical sending of the measures or calculations data. 
More detailed particulars on the methods and proceedings of measuration and 
computation can be found in the reports drawn up by each centre and contained in 
chapter Y. 
The calendar established at the London meeting and shown in paragraph 2 
could not be followed by all the Centres for different reasons. However, at the beginning 
of 1962, a good number of results had already arrived at the Presidency that, according 
to the engagements, would execute the comparisons between the adjusted photogram- 
metric coordinates of the control points and the topographic coordinates of the same 
points. 
The work appeared really very difficult: repeated checks went on till the beginning 
of Summer. The last comparisons could be done only by the end of Summer, since 
the results of the tests 19 and 20 arrived at the Presidency only in August. 
However, in the Summer of 1962, the physiognomy of the work was already 
completely defined and, by mutual consent of the Working Centres, the Presidency 
decided to hold a meeting of the Group in Milano, on October 1st, 1962. 
After an intense exchange of information between the Presidency and the Centres, 
the meeting was held in Milano in the afternoon of the 1st October of 1962, at the Insti 
tute of Geodesy, Topography and Photogrammetry of the Politechnical School. 
The President of the Group, prof. G. Cassinis, acted as chairman. The following 
persons were present: