variations as potential sources of error in making or interpreting shoreline 

 change maps. Chapter 5 contains a more detailed discussion of aerial 

 photograph analysis. 



Satellite Remotely Sensed Data 



Satellite data are available from U.S. agencies, the French Systeme Pour 

 l'Observation de la Terre (SPOT) satellite data network, and from Soviet 

 coverage 1 . In most instances, the data can be purchased either as photo- 

 graphic copy or as digital data tapes for use in computer applications. 

 Imagery and digital data may assist in understanding large-scale phenomena, 

 especially processes that are indicators of geologic conditions and surface 

 dynamics. Agencies that collect and distribute satellite data are listed in 

 Appendix C. 



Satellite data are especially useful for assessing large-scale changes in the 

 coastal zone. In the vicinity of deltas, estuaries, and other sediment-laden 

 locations, the determination of spatial patterns of suspended sediment concen- 

 tration can be facilitated with remote sensing (Figure 13). In shallow-water 

 depths of non-turbid water bodies, some features of the offshore bottom, in- 

 cluding the crests of submarine bars and shoals, can be imaged. On a rela- 

 tively crude level, satellites may assist in monitoring tidal changes, 

 particularly where the land-sea boundary changes several hundreds of meters. 

 The spatial extent of tidal flows may also be determined using thermal infra- 

 red data, which can be helpful in distinguishing temperature differences of ebb 

 and flood flows and freshwater discharges in estuaries (Figure 14). In deeper 

 waters, satellites can also provide data on ocean currents and circulation 

 (Barrick, Evans, and Weber 1977). Aircraft-mounted radar data also show 

 considerable promise in the analysis of sea state. 



The Landsat satellite program was developed by the National Aeronautics 

 and Space Administration with the cooperation of the U.S. Department of the 

 Interior. When it began in 1972, it was primarily designed as an experimental 

 system to test the feasibility of collecting earth resources data from unmanned 

 satellites. Landsat satellites have used a variety of sensors with different 

 wavelength sensitivity characteristics, ranging from the visible (green) to the 

 thermal infrared with a maximum wavelength of 12 micrometers (jam). Fig- 

 ure 15 shows bandwidths and spatial resolution of various satellite sensors. 

 Of the five Landsat satellites, only Landsat-4 and Landsat-5 are currently in 

 orbit. Both are equipped with the MSS (multispectral scanner), which has a 

 resolution of 82 m in four visible and near-infrared bands, and the thematic 

 mapper, which has a resolution of 30 m in six visible and near- and 



Russian Sojuzkarta satellite photography data are available from Spot Image Corporation 

 (Appendix C). Almaz synthetic aperture radar data are available from Hughes STX 

 Corporation. 



Chapter 2 Secondary Sources of Coastal Information 



23 



