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U.S. Department of the InteriorU.S. Geological Survey
Multispectral Remote Sensing of Benthic
Environments
Christopher Moses, Ph.D.Jacobs Technology - USGS
NPS-USGS Servicewide Benthic Habitat Mapping WorkshopJune 3-5, 2008Lakewood, CO
Outline Matters of scale Advantages and disadvantages Common principles Satellites Coral reefs applications
Scales of benthic mapping
Organism
Community
Island and coastal geomorphology
Global ecosystem distribution
Advantages and disadvantages Synoptic Repeated acquisition
Possible time series and change detection
Multi-spectral to hyperspectral
Calibration and validation Expensive Clouds High-tech issues
Rapid change, hard to follow literature
Interpretation Products based on many
assumptions Programming errors Unknown calibration
problems Unknown orbit or sensor
errors
WAVELENGTHS (IN METERS)
10-11 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 101 102
VISIBLE
GAMMA RAYS X RAYSULTRA VIOLET INFRARED
MICROWAVE
RADIO WAVES
400 500 600 700 nanometers
longershorter
A sensor measures the amount of light being reflected or emitted by the earth’s surface at specific
wavelengths in the electromagnetic spectrum
Electromagnetic Spectrum
Irradiance Radiance
Attenuation due toabsorption and scattering
in water
Ocean
Cloud
Sea Surface
Atmosphere
Path radiance
Scattering at edgesof atmosphere
Attenuation due toabsorption and
scattering in atmosphere
Radiative Transfer Theory
3
4
5
6
7
8
9
10
1994 1995 1996 1997 1998 1999 2000
Scalar Wind [m/s]
SatelliteAirport
Temporal resolution
3
4
5
6
7
8
9
10
1994 1995 1996 1997 1998 1999 2000
Scalar Wind [m/s]
SatelliteAirport
Satellites by name Landsat 7 ETM+
30 m spatial resolution 16 day revisit time, identical scene locations, LTAP NIR, R, G, B bands
ASTER Advanced Spaceborne Thermal Emission and Reflection Radiometer 15 m spatial resolution 16 day revisit time NIR, R, G (no blue!)
IKONOS 4 m spatial resolution Image acquisition by request NIR, R, G, B $$
Satellite accuracy (supervised)
L7 = 86.2 (±2.3%) 5 classes
Need class separability Sand is most easily
misclassified
Not just for corals!
http://gis.esri.com/library/userconf/proc01/professional/papers/pap900/p90011.jpg
http://www.nasa.gov/centers/goddard/earthandsun/nps_data.html
Summary I Advantages of satellites:
Synoptic; repeated acquisition; multi- or hyperspectral bands
Disadvantages: Expensive; rapidly evolving technologies; complications of
interpretation
Resolution depends on mapping needs Temporal and spatial resolution
Useful satellites for benthic mapping Landsat 7 ETM+ (30 m spatial resolution) ASTER (15 m spatial resolution)
No blue band!
IKONOS (4 m spatial resolution)
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