reefs. Advances in technology relate to changes to the spatial, spectral and
radiometric dimensions of imaging sensors on airborne or satellite platforms, and
the capabilities of the platforms themselves. The Committee on Earth Observation
Satellites (CEOS), a global collective of scientists building and using satellites to
map and monitor earth’s ecosystems, maintains an online database of all current
and planned sensors, along with their dimensions and links to data download sites
(known as the Mission, Instruments and Measurements database, which can be
found at http://database.eohandbook.com/).
1.4.1 Technological Advances
Improvements in available spatial dimensions of multispectral and hyperspectral
imaging sensors will continue to fill the scale-gaps evident in Fig. 1.4, providing
the potential for global-scale coverage of images with varying pixel sizes:
0.05–0.5 m (digital aerial photography), 0.5–10 m (high spatial resolution satellites), 10–100 m (moderate spatial resolution satellites), and 100–1,000 m (low
spatial resolution satellites).
Improvements in spectral dimensions will remain predominantly in the multispectral domain, with satellite imaging sensors continuing to move beyond the
traditional four band set (blue-green–red and NIR) towards 10–20 spectral band
sets designed to address specific environmental applications and to maximize
sensor sensitivity. Hyperspectral sensors will continue to be used mainly from
airborne platforms, while several long awaited satellite systems will be launched in
2012–2015, providing moderate spatial resolution global hyperspectral coverage
(EnMAP, HyspIRI). In all cases, sensor radiometric resolution and radiometric
calibration consistency will also be improved, allowing increased detection of
reflectance/absorption differences and more accurate detection of changes in image
time-series.
The temporal dimensions, or repeat frequency, of satellite imaging systems will
continue to be expanded; most single sensor/platform high spatial resolution systems already provide almost daily repeat acquisition. This is made possible by use
of pointable imaging sensors and more agile satellite platforms (e.g., GeoEye-1,
Worldview 2), as well as systems with constellations of multiple satellite platforms
of the same sensor. Daily repeat coverage of an area maximizes the user’s ability to
collect cloud-free, low-wind, low-wave and low-sunglint coral reef images.
Associated advances in image storage, search/archive capacity across networks,
and more frequent use of open access software and image archives is providing
users with greater ability to locate, check and download archive satellite image data
from coral reefs around the world. Acquisition of new images, especially airborne
or high spatial resolution imagery, is currently still confined primarily to research or
commercial service providers. Advances in GPS and digital photography, especially in terms of low-cost, accurate, waterproof systems has allowed field survey
1 Visible and Infrared Overview
23
radiometric dimensions of imaging sensors on airborne or satellite platforms, and
the capabilities of the platforms themselves. The Committee on Earth Observation
Satellites (CEOS), a global collective of scientists building and using satellites to
map and monitor earth’s ecosystems, maintains an online database of all current
and planned sensors, along with their dimensions and links to data download sites
(known as the Mission, Instruments and Measurements database, which can be
found at http://database.eohandbook.com/).
1.4.1 Technological Advances
Improvements in available spatial dimensions of multispectral and hyperspectral
imaging sensors will continue to fill the scale-gaps evident in Fig. 1.4, providing
the potential for global-scale coverage of images with varying pixel sizes:
0.05–0.5 m (digital aerial photography), 0.5–10 m (high spatial resolution satellites), 10–100 m (moderate spatial resolution satellites), and 100–1,000 m (low
spatial resolution satellites).
Improvements in spectral dimensions will remain predominantly in the multispectral domain, with satellite imaging sensors continuing to move beyond the
traditional four band set (blue-green–red and NIR) towards 10–20 spectral band
sets designed to address specific environmental applications and to maximize
sensor sensitivity. Hyperspectral sensors will continue to be used mainly from
airborne platforms, while several long awaited satellite systems will be launched in
2012–2015, providing moderate spatial resolution global hyperspectral coverage
(EnMAP, HyspIRI). In all cases, sensor radiometric resolution and radiometric
calibration consistency will also be improved, allowing increased detection of
reflectance/absorption differences and more accurate detection of changes in image
time-series.
The temporal dimensions, or repeat frequency, of satellite imaging systems will
continue to be expanded; most single sensor/platform high spatial resolution systems already provide almost daily repeat acquisition. This is made possible by use
of pointable imaging sensors and more agile satellite platforms (e.g., GeoEye-1,
Worldview 2), as well as systems with constellations of multiple satellite platforms
of the same sensor. Daily repeat coverage of an area maximizes the user’s ability to
collect cloud-free, low-wind, low-wave and low-sunglint coral reef images.
Associated advances in image storage, search/archive capacity across networks,
and more frequent use of open access software and image archives is providing
users with greater ability to locate, check and download archive satellite image data
from coral reefs around the world. Acquisition of new images, especially airborne
or high spatial resolution imagery, is currently still confined primarily to research or
commercial service providers. Advances in GPS and digital photography, especially in terms of low-cost, accurate, waterproof systems has allowed field survey
1 Visible and Infrared Overview
23