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These data describe the extent of floating kelp beds (Nereocystis luetkeana and Macrocystis pyrifera) in 1992 along the Strait of Juan de Fuca and outer coast of Washington State. Data are derived from photo interpretation of low tide aerial photography in the late summer, the season of maximum extent. Polygons represent bed extent or planimeter, which include the kelp canopy floating on the surface and small gaps between plants (25 meter threshold for delineating discrete beds). These data are part of a long term monitoring effort that surveys the kelp canopies annually. The entire data set is comprised of the following components: yearly inventories (feature classes) starting in 1989, excluding 1993 (kelpYYYY), a combined inventory from all years (kelp_all_years), a combined inventory of kelp observations from the five most recent years (kelp_recent_5yr), a spatial index delineating the geographic extent of monitoring sub-areas (map_index) and tabular data describing kelp characteristics for each year that link to the spatial index (summary_kelp_stats). Users who wish to use the most precise inventory estimates and compare area over multiple years should use the tabular summary tables which summarize area by map_index. The tabular estimates are more precise because they are based on the source imagery. The area estimates in the feature classes reflect subsequent processing. Methods of subsequent processing have varied with changes in technology since 1989, resulting in noticeable differences among years in the spatial data that preclude detailed comparison of spatial data across years. Major methodological changes include: 1) a format change from vector (CAD) in 1989 to raster (20 m cell size) in 1994; 2) In 2010, the resolution changed from 20 meter to 4 meter resolution. |