Mapping intertidal eelgrass (Zostera marina L.) in three coastal estuaries of the Pacific Northwest USA using false colour near-infrared aerial photography

摘要

This study describes a hybrid technique of digitally classifying aerial photography used for mapping the intertidal habitat of eelgrass (Zostera marina L.) in Pacific Northwest USA estuaries. The large tidal range (2-3 m) in this region exposes most of this seagrass community at low tide, permitting the use of false colour near-infrared film that provides good contrast in imaging vegetated intertidal habitats. Three Oregon coastal estuaries in the USA were surveyed in 2004 or 2005 at photoscales of 1:10 000 or 1:20 000. Spatial resolution was 0.25 m and the minimum mapping unit was 2.5 × 2.5 m. Spatial accuracy was within 1.5 m. Comparison of the image classification and ground survey results yielded overall classification accuracies of 83% to 97%. This appears to be an effective technique for mapping intertidal eelgrass distributions in turbid coastal estuaries with large tidal ranges.