watersurfaces_refpoints: reference points for the watersurfaces_hab polygons

watersurfaces_refpoints is a data source that reflects spatial points in the Belgian Lambert 72 coordinate reference system (EPSG-code 31370). Each point uniquely represents one polygon of the watersurfaces_hab data source. watersurfaces_refpoints is designed to 'only grow', i.e. rows are added to represent new polygon_id values from new watersurfaces_hab versions, and rows from a previous version are kept. Care is taken to recycle the same point for different polygon_id values if the latter represent the same location across different watersurfaces_hab versions. The data source is composed of two text files, watersurfaces_refpoints.tsv and watersurfaces_refpoints.yml, written by the R package git2rdata. The corresponding R data frame can be reproduced using the same package. See R-code in the 'n2khab-mhq-design' GitHub repository for the creation starting from a previous version (not stored at Zenodo), and from version watersurfaces_hab_v4 of the watersurfaces_hab data source. A reading function is provided by the R-package n2khab to return the data source in a standardized way in the R environment, either as a data frame or as a spatial object, by default filtered according to a specific version of watersurfaces_hab. Columns of the dataset: polygon_id: the polygon_id from watersurfaces_hab, either version watersurfaces_hab_v4 or older grts_ranking: the GRTS address of the point as derived from the GRTSmaster_habitats data source in_object: did the point fall within the corresponding polygon at the time of creation? Note that the polygon's geometry may have changed since then; it may not currently hold. x: easting coordinate of the point (EPSG:31370) y: northing coordinate of the point (EPSG:31370)watersurfaces_refpoints 是一个数据源，收录采用比利时兰伯特72坐标参考系统 (coordinate reference system)、EPSG代码31370的空间点，每个点唯一对应 watersurfaces_hab 数据源的一个多边形。 watersurfaces_refpoints 采用"仅追加增长"的设计原则：即仅新增数据行以对应 watersurfaces_hab 新版本中的新增 polygon_id 值，同时保留旧版本的所有数据行。若不同版本的 watersurfaces_hab 中，不同 polygon_id 对应同一地理位置，则会谨慎复用同一个点来表示。 该数据源由两个文本文件构成：watersurfaces_refpoints.tsv 与 watersurfaces_refpoints.yml，由 R 包 git2rdata 生成。使用该包即可复现对应的 R 数据框。 可参考"n2khab-mhq-design"GitHub 仓库中的 R 代码，了解如何基于旧版本（未存储于 Zenodo）及 watersurfaces_hab 数据源的 watersurfaces_hab_v4 版本生成该数据源。 R 包 n2khab 提供了专属读取函数，可在 R 环境中以标准化格式返回该数据源，支持返回数据框或空间对象，默认会根据 watersurfaces_hab 的指定版本进行数据过滤。 数据集的字段如下： polygon_id：来自 watersurfaces_hab 的 polygon_id，可对应 watersurfaces_hab_v4 或更早版本。 grts_ranking：该点的 GRTS 地址，源自 GRTSmaster_habitats 数据源。 in_object：数据生成时，该点是否位于对应多边形内部？需注意，自生成后多边形的几何形状可能已发生变更，当前该点可能不再位于多边形内。 x：该点的东向坐标（EPSG代码31370）。 y：该点的北向坐标（EPSG代码31370）。