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Map index point data are centroids (points) of the map index polygons. Map index polygons are spatial boundaries that define sub-areas in kelp bed mapping. The purpose of the sub-areas is to subdivide the study area into smaller units for analysis. Boundaries are primarily based on geographic features, such as headlands. Map index areas are used to track the abundance, species composition and distribution of of floating kelp beds (Nereocystis luetkeana and Macrocystis pyrifera) along the Strait of Juan de Fuca and outer coast of Washington State. These data are part of a long term monitoring effort that surveys kelp canopies in this area 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 (polygon and point feature classes) delineating the geographic extent of monitoring sub-areas (map_index, map_index_pts), 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. |