A modified version of the RICS specification was presented to 
and adopted by the ISPRS at the Rio Congress in 1984, for a 
four year trial period. In 1987 a small working group was set 
up in the UK to review the specification adopted at Rio and to 
make recommendations for Kyoto, in the light of differences of 
opinion encountered by users of the aerial photography 
specifications that have become apparent in recent times. 
Both the RICS and the ISPRS specifications contain six 
sections and although minor differences in the wording occur 
throughout, differences of substance are found in only four 
clauses. These four clauses form the basis of the 
questionnaire. 
The Questionnaire 
The questionnaire was sent to 70 countries for the attention 
of the Commission 1 correspondents. Twelve replies were 
received. A further two questionnaires were received from 
delegates to the Commonwealth Survey Officers Conference, held 
at Cambridge University, England August 1987, where delegates 
were invited to complete questionnaires. Not all respondents 
answered all questions. The questionnaire was designed to 
discover the extent to which vertical photography 
specifications were known and used and in particular, to 
discover whether users preferred the ISPRS specification, the 
RICS specification or a compromise on the four clauses where 
differences of opinion are known to exist. 
The results show that 65$ of respondents were familiar with 
the ISPRS specification compared with 43% for the RICS 
specification. 43% had used the ISPRS specification, but only 
14% had used the RICS specification. 
In Section 2.1.1. concerning residual distortion of the 
metric camera calibration, the RICS specification calls for 
"not more than 15 micrometres within 140 mm of the principal 
point" whereas the ISPRS offers a choice of three values: 
10/15/20 micrometres. 79% favoured the single value suggested 
by the RICS specification against only 7% for the ISPRS triple 
option. 
In Section 2.2.1. concerning the frequency at which metric 
camera calibration must be carried out, opinion is more evenly 
divided with 36$ in favour of the one year in RICS and 43$ for 
the two years in ISPRS. 
In Section 2.2.3. concerning the intervals for the 
measurement of radial distortion along the diagonals of the 
format, RICS calls for "not less than 20 mm", while the ISPRS 
requires "not less than 25mm". 79$ were in favour of the 
smaller interval with only 14$ in favour of the larger ISPRS 
interval. 
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