Thanks to Gordon Andreassend for explaining its history to me:
Aerial photography really falls into two categories:
- The use of a hand-held camera produces record photography, and consists of single shots.
- Aerial survey work requires a bigger camera mounted within the aircraft that is capable of taking a series of photographs that overlap by at least 50% (usually 60%). It is this overlap area that provides the cover required to obtain the stereo image.
The 1924 RAF photography was required for mapping, and was carried out as an aerial survey.
No further aerial survey photography was recorded until the 1963 survey for mapping was carried out by Huntings (a UK company).
Huntings returned once or twice in the 60's to capture more stereo photography, and it was not until 1968 that the HK Survey Office was able to carry out limited air survey work using an old air survey camera. That camera was lost in a plane crash in 1970, and in 1972, a new modern camera fitted in a twin-engined aircraft provided all the photography needed for the mapping of Hong Kong. The cameras have been upgraded over the years, but that aerial survey coverage exist to this day, and is handled by the SMO, using GFS aircraft.
All other photography from the air can only be considered as record photography, and we do know that such coverage was obtained by the RAF from 1924 until 1945, but was not recorded in Hong Kong.
Immediately after the war the RAF captured the record photography that is now held by the SMO. The RAF handed over all negatives they had at the time of the handover. The only complete record of this later RAF photography is that which the RAF took after about September 1945.
Gordon also explains his own involvement in this field:
After starting as a NZ-trained Land Surveyor, I worked in Australia and UK then came to HK on a 3 year contract in March 1966. HK was supposed to be a stepping stone back to NZ ! However, the work was interesting and 3 years became 30 ! I started work as an engineering surveyor, and as I had learnt to fly in Australia the boss thought I would be good to take on the job of flying in the Auxilliary Airforce on aerial survey.
At about the same tme I moved into the Survey Office to become the Cartographer - only one post at that time. The learning curve went up - and I signed on as permanent staff to move gradually up to the top slot of Govt. Land Surveyor, Head of the SMO, post now graded as Dep Director, Lands Dept.
Retired in 1995 - and still in HK !!