Image combination techniques were applied to merge each
pair of true color and infrared digitized photographs into
one imagery file (Kuchler, 1984).
While, the near infrared image can penetrate only 1 m
of water, the detail of reef flat morphology noted above
is very apparent (Figure 3) and it complements the 15–
20-m-depth penetration of the color image. Advantages
are high resolution, choice of timing (though weather
dependent), and modest cost. In an initial experiment mapping Marine Park coral reefs in Thailand for management
purposes, it was possible to differentiate between reef flat
head and branching corals, seagrass beds and nonliving
substrate, with an accuracy between 86.7% and 100%
(Thamrongnawasawat and Hopley, 1995). Mumby and
Green (2000) provide a critique of the digitized aerial photographic methodology, concluding that it is ideally suited
to small area survey.
However, as the resolution and spectral cover of satellite imagery has progressed, it too has the ability to provide ecological data appropriate to management
requirements (Mumby and Green, 2000). For the differentiation of ecological zones across reef tops, the latest digital airborne scanners, e.g., the Compact Airborne
Spectrographic Imager (CASI), benefitting from the lowlevel aircraft platforms of aerial photography and the
sophisticated scanning technology of satellites, are now
arguably the most effective (Mumby and Green, 2000).
Its spectral resolution is at least equal to that of satellite
imagery. Spatial resolution is also high though dependent
on flying height (e.g., from 840 m it is 1 m). Depth penetration can be >18 m. In a comparison of techniques for
mapping reefal habitats, Mumby and Green (2000) quote
81% accuracy for CASI compared with the levels of
57% for 1:10,000 color aerial photography and <37%
for satellite imagery.
Over the last 20 years, the various types of remote sensing have complemented each other. Advances in the analysis techniques for digitized aerial photography has
largely come from satellite imagery (see Andrefouet and
Riegl, 2004), and sophisticated airborne scanners have
combined the advantages of these complementary techniques. Coral reef science has benefitted from remote
sensing for almost 100 years. Among all the aerial remote
sensing techniques, aerial photography still has the finest
resolving power. For example, further experiments by
Hopley and Catt (1988) on Cape Tribulation reefs
(GBR) used photography from as low as 500
0 (152 m),
producing images with a pixel size of only 7 Â 7 cm, sufficient to differentiate between major groupings of corals
and other organisms. The main disadvantage is the size
of the data bank resulting from the very high resolution.
Nonetheless, aerial photography remains an important
tool for documenting the physical and ecological complexity of coral reef habitat, especially when the scale
and resolution are geared to the specific needs of the
project with which it is associated (see also Remote
Sensing).
Bibliography
Andrefouet, S., and Riegl, B. (eds.), 2004. Remote sensing of coral
reefs. Coral Reefs, 23(1), 1–168. (n.b. issue devoted to remote
sensing with examples of integrating satellite and aerial photo
data and extensive references).
Hopley, D., 1978. Application of aerial photography and other
remote sensing techniques to coral reef research. In Stoddart,
D. R., and Johannes, R. E. (eds.), Handbook of Coral Reef
Research Methods. Paris: UNESCO, pp. 23–44.
100 m
Aerial Photography of Coral Reefs, Figure 2 Color near the
infrared photograph from $5,000
0
(1,524 m) of Wheeler Reef
near Townsville on the Great Barrier Reef. Tide was a Spring low
and features on the reef margin with healthy coral cover show
a stronger reflectance than those on the main reef flat, where ca.
0.25 m water cover reduces the IR penetration.
100 m
Aerial Photography of Coral Reefs, Figure 3 Color near the
infrared photograph of Pandora Reef near Townsville, GBR on
a medium low tide. The full tonal range of the IR reflectance is
used on the features, which are exposed or have a water cover of
$1 m including living coral margins, shingle ridges, and reef flat
pools with depths up to 1 m.
14
AERIAL PHOTOGRAPHY OF CORAL REEFS
pair of true color and infrared digitized photographs into
one imagery file (Kuchler, 1984).
While, the near infrared image can penetrate only 1 m
of water, the detail of reef flat morphology noted above
is very apparent (Figure 3) and it complements the 15–
20-m-depth penetration of the color image. Advantages
are high resolution, choice of timing (though weather
dependent), and modest cost. In an initial experiment mapping Marine Park coral reefs in Thailand for management
purposes, it was possible to differentiate between reef flat
head and branching corals, seagrass beds and nonliving
substrate, with an accuracy between 86.7% and 100%
(Thamrongnawasawat and Hopley, 1995). Mumby and
Green (2000) provide a critique of the digitized aerial photographic methodology, concluding that it is ideally suited
to small area survey.
However, as the resolution and spectral cover of satellite imagery has progressed, it too has the ability to provide ecological data appropriate to management
requirements (Mumby and Green, 2000). For the differentiation of ecological zones across reef tops, the latest digital airborne scanners, e.g., the Compact Airborne
Spectrographic Imager (CASI), benefitting from the lowlevel aircraft platforms of aerial photography and the
sophisticated scanning technology of satellites, are now
arguably the most effective (Mumby and Green, 2000).
Its spectral resolution is at least equal to that of satellite
imagery. Spatial resolution is also high though dependent
on flying height (e.g., from 840 m it is 1 m). Depth penetration can be >18 m. In a comparison of techniques for
mapping reefal habitats, Mumby and Green (2000) quote
81% accuracy for CASI compared with the levels of
57% for 1:10,000 color aerial photography and <37%
for satellite imagery.
Over the last 20 years, the various types of remote sensing have complemented each other. Advances in the analysis techniques for digitized aerial photography has
largely come from satellite imagery (see Andrefouet and
Riegl, 2004), and sophisticated airborne scanners have
combined the advantages of these complementary techniques. Coral reef science has benefitted from remote
sensing for almost 100 years. Among all the aerial remote
sensing techniques, aerial photography still has the finest
resolving power. For example, further experiments by
Hopley and Catt (1988) on Cape Tribulation reefs
(GBR) used photography from as low as 500
0 (152 m),
producing images with a pixel size of only 7 Â 7 cm, sufficient to differentiate between major groupings of corals
and other organisms. The main disadvantage is the size
of the data bank resulting from the very high resolution.
Nonetheless, aerial photography remains an important
tool for documenting the physical and ecological complexity of coral reef habitat, especially when the scale
and resolution are geared to the specific needs of the
project with which it is associated (see also Remote
Sensing).
Bibliography
Andrefouet, S., and Riegl, B. (eds.), 2004. Remote sensing of coral
reefs. Coral Reefs, 23(1), 1–168. (n.b. issue devoted to remote
sensing with examples of integrating satellite and aerial photo
data and extensive references).
Hopley, D., 1978. Application of aerial photography and other
remote sensing techniques to coral reef research. In Stoddart,
D. R., and Johannes, R. E. (eds.), Handbook of Coral Reef
Research Methods. Paris: UNESCO, pp. 23–44.
100 m
Aerial Photography of Coral Reefs, Figure 2 Color near the
infrared photograph from $5,000
0
(1,524 m) of Wheeler Reef
near Townsville on the Great Barrier Reef. Tide was a Spring low
and features on the reef margin with healthy coral cover show
a stronger reflectance than those on the main reef flat, where ca.
0.25 m water cover reduces the IR penetration.
100 m
Aerial Photography of Coral Reefs, Figure 3 Color near the
infrared photograph of Pandora Reef near Townsville, GBR on
a medium low tide. The full tonal range of the IR reflectance is
used on the features, which are exposed or have a water cover of
$1 m including living coral margins, shingle ridges, and reef flat
pools with depths up to 1 m.
14
AERIAL PHOTOGRAPHY OF CORAL REEFS