A large percentage of the global population lives in coastal regions. Consequently, these areas are under intense pressure from urban growth, industry and tourism. A prerequisite for sustainable management of these environmentally sensitive areas is the availability of accurate and up-to-date information on their extent, state and rate of change.

Earth-observation satellites, such as RADARSAT-1, are excellent tools for collecting information in support of coastal zone management as they can provide synoptic or detailed information of a region on a regular basis. With its higher resolution, multi-polarization and fully polarimetric data, RADARSAT-2 will offer a new look at the coastal zone. Studies on the use of multi-polarized and fully polarimetric C-band radar data for coastal zone mapping are underway. The following reports describe some of the results.

Polarimetric SAR for Geomorphic Mapping in the Inter Tidal Zone, Minas Basin, Bay of Fundy, Nova Scotia.,
C. Hugenholtz and J van der Sanden,
Natural Resources Canada, CCRS.
Nov. 2001.

For full paper, click here to link to the CCRS Bibliographic Database

Summary of Report
On average, the HH and HV channels were found to display a higher backscatter contrast between water and land than the VV and circularly polarized channels. Results reported in literature indicate that the HV backscatter is less sensitive to incidence angle and wind effects than the HH backscatter. Hence, the cross-polarized channel can be expected to offer the most potential for shoreline extraction. Multi-polarization and full polarimetric data were shown to offer significantly more potential for mapping coastal zone characteristics, including substrate and vegetation types, than HH-polarized data. The data studied were acquired by the airborne Convair-580 SAR system. The results provide some indication of the capabilities of the RADARSAT-2 system.

Figure 6a - Figure 6b - Figure 6c - Figure 6d: RGB color composite (R-HH, G-HV, B-VV) and three linear polarizations (VV, HH, and HV respectively) for Evangeline Beach mudflat. A) RGB, B) VV, C) HH, and D) HV.

Figure 9: Plot of backscatter values along a portion of the Evangeline mudflat. Relative locations of different geomorphic targets have been verified during field visits. Backscatter transect denoted in Figure 6. Curves derived from averaging in azimuth by 200 samples per line.

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.