Additive color process using SAR amplitude images

Released: Nov. 20, 2013 Japanese version of this page

Extraction of shoreline changes by an additive color process using SAR images

A SAR amplitude image is expressed with a gray scale corresponding to microwave backscatter intensity from the Earth surface. In general, white/black color in SAR amplitude image means strong/weak reflection, respectively. The intensity depends on the roughness of the surface. The reflection from land area is much stronger than that from sea area because the terrene is rough while the sea surface is smooth. Using this features of SAR image, we can detect shoreline changes from changes of the roughness.
In order to automatically determine regions of backscatter changes, a three-color attribute is applied. In this analysis, we first assign intensity variations in the pre-seismic amplitude image to variations in cyan; (R, G, B) = (0 %, 100 %, 100 %), and then variations in the post-seismic image to red; (R, G, B) = (100 %, 0 %, 0 %). Combining these two images, areas where backscatter increased (land emergence) / decreased (land submergence) / unchanged turn out to be red, cyan, and gray, respectively.

additive color process