National Geo-spatial Information (NGI) is the government component responsible for aerial photography and has an archive of aerial photographs dating back to the 1930's. The photography is at a variety of scales and has provided complete coverage of the country since the 1950's. These are all vertical aerial phtographs taken from aircraft. Photography is continuously reflown to provide new photography for ongoing map revision and for sale to users.
Unlike a generalised line map, almost all detail is visible on an aerial photograph. The user, although unable to make accurate measurements on the photograph, is able to perform his or her own interpretation of what exists on the ground. Aerial photographs are also an historic record of what existed at the time the photograph was taken.
Modern aerial photographs are a standard contact size of 23 x 23cm. Enlargements of up to three times a photograph area are available. Overlapping stereopairs may be purchased for stereo viewing, providing the user with a 3-dimensional image. Colour photography is also available in selected areas.
A short history of Film based analogue photography
Since 1936, NGI, known then as Trig Survey has been authorised to undertake aerial survey work and to provide itself with the necessary equipment and staff to achieve this mandate.
By 1950 the entire country had been covered with aerial photography. The imagery was captured at a photo-scale of 1:30 000 and flown at a height of approximately 4570m above ground level. In the 1960's a super wide-angle camera was used, enabling the photography to be captured smaller scales without the loss of accuracy. This meant a larger area was covered by each photo, therefore fewer photos were required and production time decreased.
In 1970, the government decided that ultra-small scale photography at a scale of 1: 150 000 would be flown, to re-map the contours and adjust for the change to the metric system.
NGI continued to capture analogue photography throughout the country every 4-7 years until 2008 when it was decided to upgrade to a digital sensor system.