How To Handle Clouds - Shoreline Obscurers
Eiao - Image Showing Questionable Area(S-07-05_2000)As I digitized this shoreline, I came across what looked like a small bay. The WVS map files do not show a bay in this area. Without giving the feature too much thought, I digitized, mapped and finalized my product.
Eiao - Map Showing Questionable Area I looked at the finished map and pondered my decision. "If WVS doesn't show a bay, what could this 'bay' actually be?" The Landsat image is peppered with clouds. If you look closely at the map of Eiao, in the previous post, the green shorelines are classified as part of the EVS Shoreline Obscured layer. I studied the image closely and looked at the small cloud located SE of the bay. After determing that the shadows cast by all clouds display a distinct ground signatures - black shadow, which obscures all ground features beneath it and the shadow is cast in a NW direction from its originating cloud. I realized that the small bay was, most likely, a cloud shadow. I redigitized the shoreline and classified the reworked area as EVS Shoreline Obscured.
Eiao - Map with Corrected AreaThe redigitized shoreline is displayed above. Now, you ask, is this the actual shoreline? No, maybe, sure? In other words, I don't know yet. When I can study another image (Space Shuttle, map) of the island, I should be able to recast the shoreline into its proper layer (EVS Shoreline). Until that time, this cloud-shadow-obscured-shoreline is just that.
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