1. U.S. Department of the Interior U.S. Geological Survey 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 Organism Community Island and coastal geomorphology Global ecosystem distribution

4. 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

5. 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 10 1 10 2 VISIBLE GAMMA RAYS X RAYS ULTRA 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

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

7. Satellite Airport Temporal resolution Satellite Airport

8. Landsat ASTER Ikonos AISA 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. North Florida Reef Tract Landsat 7 ETM+ 5 Feb 2000

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