2.2 Photography of Coral Reefs
Fixed-wing or rotary aircraft are the most common platforms from which to collect
low-altitude photographs. However, other platforms have also been useful in coral
reef studies. Rützler (1978) attached a camera to an aluminum frame that was
suspended from a tethered helium balloon to successfully collect images at an
altitude of 50 m above Carrie Bow Cay, Belize. Scoffin (1982) suspended a radiooperated camera from the cord of a kite to collect vertical and oblique photographs
at altitudes from 50 to 200 m over reef flats in the Cook Islands. Such low-cost
methods are shown to be especially useful in locations where winds of 7–25 knots
might occur, such as those commonly found around tropical islands exposed to the
trade winds.
High-altitude photographs of Earth taken by astronauts from the windows of
spacecraft, such as the International Space Station and the Space Shuttle, have also
played a role in studying coral reef ecosystems. The photographs are in the public
domain from NASA’s Office of Earth Sciences at the Johnson Space Center (http://
eol.jsc.nasa.gov). Robinson et al. (2000) estimate that nearly 30,000 of over
375,000 photographs in the database at that time had potential value for coral reef
studies (e.g., not over- or under-exposed, not too oblique, and with limited sunglint). As of October 2011, the database contains over one million photographs of
Earth. If the percentage (8 %) estimated by Robinson et al. (2000) holds true, the
number of photographs with potential value for coral reef studies may now be as
high as 80,000. Cloud cover is often a problem when acquiring images in tropical
regions using commercial satellites with pre-determined orbits. However, because
astronauts can be visually selective when collecting images, photographs acquired
in this manner over coral reef areas tend to have low or no cloud cover (Robinson
et al. 2000). Astronaut-acquired photographs provide a low-cost alternative to
commercial imagery, which can be important for developing countries, and can be
used stand-alone or for supplementing analyses using other data sources (Robinson
et al. 2002).
One of the most common uses of aerial photography in coral reef environments
is for mapping the location and extent of a variety of marine and coastal habitats.
Chauvaud et al. (1998) used aerial photographs for thematic mapping of marine
communities in the Bay of Robert on the island of Martinique in the French West
Indies. They state that high-resolution aerial photographs are well suited to map
the intricate complexities of tropical coastal habitats. Ekebom and Erkkilä (2003)
summarize the advantages and disadvantages of numerous remote-sensing techniques used for habitat mapping. Their test study, comparing habitat delineations
from multiple user-interpreters, concluded that the high spatial resolution of aerial
photographs provided the best data source for reliable habitat identification.
Aerial photograph collections are often acquired with an overlap ranging from
60 to 65 %, making them ideal for viewing and mapping the three-dimensional
perspective of reef morphology using stereo-pairs (Sheppard et al. 1995). Stereopairs and photogrammetry methods have also been used to calculate depths to
2 Photography Application
31
Fixed-wing or rotary aircraft are the most common platforms from which to collect
low-altitude photographs. However, other platforms have also been useful in coral
reef studies. Rützler (1978) attached a camera to an aluminum frame that was
suspended from a tethered helium balloon to successfully collect images at an
altitude of 50 m above Carrie Bow Cay, Belize. Scoffin (1982) suspended a radiooperated camera from the cord of a kite to collect vertical and oblique photographs
at altitudes from 50 to 200 m over reef flats in the Cook Islands. Such low-cost
methods are shown to be especially useful in locations where winds of 7–25 knots
might occur, such as those commonly found around tropical islands exposed to the
trade winds.
High-altitude photographs of Earth taken by astronauts from the windows of
spacecraft, such as the International Space Station and the Space Shuttle, have also
played a role in studying coral reef ecosystems. The photographs are in the public
domain from NASA’s Office of Earth Sciences at the Johnson Space Center (http://
eol.jsc.nasa.gov). Robinson et al. (2000) estimate that nearly 30,000 of over
375,000 photographs in the database at that time had potential value for coral reef
studies (e.g., not over- or under-exposed, not too oblique, and with limited sunglint). As of October 2011, the database contains over one million photographs of
Earth. If the percentage (8 %) estimated by Robinson et al. (2000) holds true, the
number of photographs with potential value for coral reef studies may now be as
high as 80,000. Cloud cover is often a problem when acquiring images in tropical
regions using commercial satellites with pre-determined orbits. However, because
astronauts can be visually selective when collecting images, photographs acquired
in this manner over coral reef areas tend to have low or no cloud cover (Robinson
et al. 2000). Astronaut-acquired photographs provide a low-cost alternative to
commercial imagery, which can be important for developing countries, and can be
used stand-alone or for supplementing analyses using other data sources (Robinson
et al. 2002).
One of the most common uses of aerial photography in coral reef environments
is for mapping the location and extent of a variety of marine and coastal habitats.
Chauvaud et al. (1998) used aerial photographs for thematic mapping of marine
communities in the Bay of Robert on the island of Martinique in the French West
Indies. They state that high-resolution aerial photographs are well suited to map
the intricate complexities of tropical coastal habitats. Ekebom and Erkkilä (2003)
summarize the advantages and disadvantages of numerous remote-sensing techniques used for habitat mapping. Their test study, comparing habitat delineations
from multiple user-interpreters, concluded that the high spatial resolution of aerial
photographs provided the best data source for reliable habitat identification.
Aerial photograph collections are often acquired with an overlap ranging from
60 to 65 %, making them ideal for viewing and mapping the three-dimensional
perspective of reef morphology using stereo-pairs (Sheppard et al. 1995). Stereopairs and photogrammetry methods have also been used to calculate depths to
2 Photography Application
31