Case Studies: Coastal Zone Monitoring

» Global Shoreline Mapping from an Airborne Polarimetric SAR, Assessment for RADARSAT 2 Polarimetric Modes.,

M. Yeremy, A. Beaudoin, J. Beaudoin, G. Walter. Defence Research Establishment Ottawa, Technical Report DREO TR 2001-056. Nov. 2001.

Summary of report:

The National Imagery and Mapping Agency (NIMA), USA and Defence Research Establishment Ottawa (DREO), Canada have been involved with a project agreement to study global shoreline mapping. This report documents the results from shoreline mapping studies using polarimetric data. Shoreline mapping requires an integration of several scientific disciplines including tidal models, SAR image geo-referencing and SAR image classification. For extracting more accurate shoreline vector waterlines, tidal variations must be considered as well as information about the shoreline slope and the land-water interface. This report discusses studies implementing polarimetric methods to extract shoreline slopes and land-water boundaries in the coastal region.

Shorelines were more difficult to extract from image signatures of coastal regions where the ocean wave dynamics were energetic. Image phenomenology was found to vary with different types of environment and for this reason should also be a consideration of the analysis. For instance, in regions where the tidal action is mild, the beach sedimentology is often significantly different from a region where the tidal activity is intense. These physical differences result in image signatures for a particular shore type.

In general, reasonable shorelines were extracted from all single channel data. However, for natural environments the HH channel was found to be optimal (e.g. Bay of Fundy) for shoreline extraction with shoreline vectors results within the experimental error. All channels provide reasonable shoreline vectors but the polarimetric data produced more robust results (between 0 and 10 m for averaged errors over 2 km). Fully polarimetric data produced better qualitative results for coastal regions where the wave action was more dynamic (e.g. North Carolina study sites). In this study, polarimetric filters such as a Pre-Whitening Filter (Novak) or the Lee polarimetric filter provided the best shoreline discrimination. Cross-polarized channels provided velocity information that improved the shoreline vector results for environments with intense wave action that results in image signatures that are difficult to analyze.

It was noted that these results could be further improved if tidal and shore slope information is included in the analysis. Beach slope extraction from the images produced promising results but requires further experiments that include ground-truthing components.

Summary of Capabilities
	Polarization				Notes
	HH	HV/VH	VV	Quad-pol
General delineation of boundaries between various tidal sub environments					Quad-pol provides better classification information.
Delineating shoreline	shallow				Single channel HH data will provide reasonable results for low dynamic coastlines. Quad-pol is suggested for more dynamic environments.
Delineation of sediment classes	shallow