WA State Floating Kelp Monitoring: Coast, Strait, Aquatic Reserves

These data are part of a long-term monitoring effort to survey floating kelp canopies annually. The dataset contains the following components: 1) layers indicating floating kelp persistence combined (persistence_all_kelp) and split by species (perstistence_bull_kelp, persistence_giant_kelp, persistence_mixed_kelp) , 2) A combined inventory from the 5 most recent years (kelp_recent_5yr), 3) A spatial index (map_index_points and map_index_polygons), 4) A summary table describing kelp characteristics for each year that link to the spatial index (summary_kelp_stats). Data are derived from photo interpretation of low tide aerial photography collected in the late summer, the season of maximum bed 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). 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.本数据集为长期监测项目的组成部分，旨在年度性开展漂浮海带冠层覆盖状况调查。数据集包含以下组成部分：1）两类持续性图层：其一为涵盖所有漂浮海带的持续性图层（persistence_all_kelp），其二为按物种划分的持续性图层，包括泡叶海带持续性图层（persistence_bull_kelp）、巨藻持续性图层（persistence_giant_kelp）与混合海带持续性图层（persistence_mixed_kelp）；2）近5年综合清查数据集（kelp_recent_5yr）；3）空间索引：地图索引点图层（map_index_points）与地图索引面图层（map_index_polygons）；4）与空间索引关联的年度海带特征汇总表（summary_kelp_stats）。本数据集数据源自夏末（海带林覆盖范围达到最大的季节）采集的低潮航空照片的目视解译（photo interpretation）。面要素代表海带林的覆盖范围（即平面测绘范围），涵盖漂浮于海面的海带冠层以及植株间的小型空隙，划定独立林床的阈值为25米。若用户希望获取最精准的清查估算结果并开展多年度面积对比，应使用按地图索引汇总面积的表格汇总表。该表格估算结果更为精准，因其直接基于原始影像数据。要素类中的面积估算值则经过了后续处理。自1989年以来，后续处理方法随技术迭代发生多次重大变更，导致不同年份的空间数据存在显著差异，无法开展跨年度空间数据的精细化对比。主要方法变更包括：1）1989年从矢量（vector）格式（计算机辅助设计CAD）变更为1994年的栅格（raster）格式，像元大小为20米；2）2010年将空间分辨率从20米调整为4米。