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Multispectral Remote Sensing of Benthic Environments

Multispectral Remote Sensing of Benthic Environments. Christopher Moses, Ph.D. Jacobs Technology - USGS NPS-USGS Servicewide Benthic Habitat Mapping Workshop June 3-5, 2008 Lakewood, CO. Outline. Matters of scale Advantages and disadvantages Common principles Satellites

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Multispectral Remote Sensing of Benthic Environments

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  1. Multispectral Remote Sensing of Benthic Environments Christopher Moses, Ph.D. Jacobs Technology - USGS NPS-USGS Servicewide Benthic Habitat Mapping Workshop June 3-5, 2008 Lakewood, CO

  2. Outline • Matters of scale • Advantages and disadvantages • Common principles • Satellites • Coral reefs applications

  3. Scales of benthic mapping Global ecosystem distribution Island and coastal geomorphology Community Organism

  4. 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 Advantages and disadvantages

  5. WAVELENGTHS (IN METERS) shorter 10-11 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 101 102 longer ULTRA VIOLET GAMMA RAYS X RAYS INFRARED RADIO WAVES MICROWAVE VISIBLE 400 500 600 700 nanometers Electromagnetic Spectrum A sensor measures the amount of light being reflected or emitted by the earth’s surface at specific wavelengths in the electromagnetic spectrum

  6. Path radiance Scattering at edges of atmosphere Attenuation due to absorption and scattering in atmosphere Attenuation due to absorption and scattering in water Irradiance Radiance Radiative Transfer Theory Cloud Atmosphere Sea Surface Ocean

  7. Satellite Airport Temporal resolution Satellite Airport

  8. AISA Ikonos ASTER Landsat Spatial resolution

  9. 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 • $$

  10. Landsat 7 ETM+ full scene ~180 km Path 18, Row 48 8 Nov. 2000

  11. Landsat 7 ETM+ Glover’s Reef

  12. Landsat 7 vs. IKONOS

  13. Photo interpretation of Glovers Reef

  14. Landsat 7 ETM+ 5 Feb 2000 North Florida Reef Tract

  15. Supervised habitat classification Brock et al. (2006)

  16. Satellite accuracy (supervised) • L7 = 86.2 (±2.3%) • 5 classes • Need class separability • Sand is most easily misclassified

  17. Benthic habitat mapping with airplanes

  18. Aerial imagery of BISC

  19. 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

  20. 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)

  21. Summary II • Landsat 7 and IKONOS can reach accuracies of >80% in reef areas • Supervised classification of 5-6 classes • Satellites and aerial photos reliable to max depth of ≤20 m • Particularly useful in reef areas, but also good for kelp and other near surface habitats

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