Further Information on Remote Sensing

Uses of sensors:

1) Satellite

• CZCS: useful for tracing plumes over long distance due to its narrow bands, very sensitive sensors and 1x1 km pixels. Has been used in studying the river Po plume into the Adriatic Sea, Italy, and dispersal of Yukon River water in Norton Sound, Alaska.

• AVHRR: useful for quantifying water quality due to its dynamic range which accommodates the high reflectance of land and coastal waters. It has the same pixel resolution of the CZCS and, like the CZCS, is useful in observing large-scale phenomena.

• Landsat and SPOT: provide pixel resolutions of 30-80 m: good spatial resolution. Useful in mapping suspended sediment and variations in water colour in coastal environments; useful for in situ observations. Disadvantages: high cost of data, long revisit times (not suitable for monitoring), SPOT and MSS lack blue bands (not suitable for quantifying aquatic chlorophyll) The Landsat was used to identify sources of suspended solids which end up in the Northeastern Gulf of Mexico. Reflectance patterns and other data were used to determine that the larger amounts suspended solids originated from the Mobile river system as well as during high wind resuspension and shoreline erosion events. Moderate to minor inputs were found to be due to small stream runoff and dredging.

2) Aircraft

• AVIRIS: approximately 20 m resolution (high). Suitable for detecting mainly highly reflective constituents in water. Suitable for monitoring aquatic pollution at small scales.

• FLI: high spatial resolution and sensitivity at longwave bands. Suitable for examining distribution of pigments in eutrophication events.

• CASI: optional imaging or spectral mode. Small size is also preferable. Good potential for documenting marine pollution cases.

• AOL: contains a laser sensor which allows for specificity of response, facilitating of signal interpretation and low altitude for operation. Useful for mapping chlorophyll and horizontal and vertical turbidity variations.

• SeaWIFS: (Sea-viewing wide-field-of-view sensor) is a more modern satellite sensor and was used to assess material transport and nutrient-derived plumes in the northern Gulf of Mexico. This technique was successful in remotely estimating nutrient and sediment loads in coastal zones.