qdgc Ecuador
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DGC tables delivered in geopackage file<br> - - - - - - - - - - - - - - - - - - - - - -<br> QDGC represents a way of making (almost) equal area squares covering a specific area to represent specific qualities of the area covered. The squares themselves are based on the degree squares covering earth. Around the equator we have 360 longitudinal lines , and from the north to the south pole we have 180 latitudinal lines. Together this gives us 64800 segments or tiles covering earth.<br> <br> <br> Within each geopackage file you will find a number of tables with these names:<br> -tbl_qdgc_01<br> -tbl_qdgc_02<br> -tbl_qdgc_03<br> -tbl_qdgc_04<br> -tbl_qdgc_05<br> -etc<br> <br> <br> The attributes for each table are:<br> qdgc Unique Quarter Degree Grid Cell reference string<br> level_qdgc QDGC level<br> cellsize degrees decimal degree for the longitudal and latitudal length of the cell<br> lon_center Longitude center of the cell<br> lat_center Latitudal center of the cell<br> area_km2 Calculated area for the cell<br> geom Geometry<br> <br> <br> Metadata<br> --------<br> Geodata GCS_WGS_1984<br> Datum: D_WGS_1984<br> Prime Meridian: 0<br> <br> <br> Areas are calculated with different versions of Albers Equal Area Conic using the PostGIS function st_area. For the African continent I have used Africa Albers Equal Area Conic which will look like this:<br> - st_area(st_transform(geom, 102022))/1000000)<br> <br> <br> Conditions<br> ----------<br> Delivered to the user as-is. No guarantees. If you find errors, please tell me and I will try to fix it. Suggestions for improvements can be addressed to the github repository: https://github.com/ragnvald/qdgc<br> <br> <br> Thankyou!<br> --------<br> The work has over the years been supported and received advice and moral support from many organisations and stakeholders. Here are some of them:<br> - TAWIRI (http://tawiri.or.tz/)<br> - Dept of Biology, NTNU, Norway<br> - Norwegian Environment Agency<br> - Eivin Røskaft, Steven Prager, Howard Frederick, Julian Blanc, Honori Maliti, Paul Ramsey<br> <br> <br> References<br> ----------<br> * http://en.wikipedia.org/wiki/QDGC<br> * http://www.mindland.com/wp/projects/quarter-degree-grid-cells/about-qdgc/<br> * http://en.wikipedia.org/wiki/Lambert_azimuthal_equal-area_projection<br> * http://www.safe.com
以地理数据包（Geopackage）格式交付的DGC数据表 - - - - - - - - - - - - - - - - - - - - - - QDGC（Quarter Degree Grid Cell，四分度网格单元）是一种通过生成近似等面积正方形格网覆盖特定区域，以表征该区域相关属性的方法。此类格网基于覆盖全球的经纬度方格生成。在赤道区域共有360条经线，从北极至南极则有180条纬线，二者组合可得到覆盖全球的64800个分区或瓦片。 每个地理数据包文件中均包含若干数据表，命名格式如下： - tbl_qdgc_01 - tbl_qdgc_02 - tbl_qdgc_03 - tbl_qdgc_04 - tbl_qdgc_05 - 以此类推 各数据表包含以下字段： qdgc：唯一四分度网格单元引用字符串 level_qdgc：QDGC层级 cellsize degrees：格网经向与纬向边长对应的十进制度数值 lon_center：格网中心经度 lat_center：格网中心纬度 area_km2：格网计算面积（单位：平方千米） geom：几何要素 元数据 -------- 地理坐标系统：GCS_WGS_1984 大地基准面：D_WGS_1984 本初子午线：0° 面积计算采用PostGIS的st_area函数结合不同版本的阿尔伯斯等面积圆锥投影（Albers Equal Area Conic）实现。针对非洲大陆，使用非洲阿尔伯斯等面积圆锥投影，计算表达式为：st_area(st_transform(geom, 102022))/1000000) 使用条款 ---------- 本数据集按现状提供，不附带任何质量保证。若发现错误，请及时告知作者以便修正。相关改进建议可提交至该GitHub仓库：https://github.com/ragnvald/qdgc 致谢 -------- 本项目多年来得到了众多机构与相关方的支持、专业建议与精神鼓励，以下为部分致谢对象： - TAWIRI（http://tawiri.or.tz/） - 挪威科技大学（NTNU）生物系 - 挪威环境署 - 艾文·罗斯卡夫特（Eivin Røskaft）、史蒂文·布拉格（Steven Prager）、霍华德·弗雷德里克（Howard Frederick）、朱利安·布兰克（Julian Blanc）、奥诺里·马利蒂（Honori Maliti）、保罗·拉姆齐（Paul Ramsey） 参考文献 -------- * http://en.wikipedia.org/wiki/QDGC * http://www.mindland.com/wp/projects/quarter-degree-grid-cells/about-qdgc/ * http://en.wikipedia.org/wiki/Lambert_azimuthal_equal-area_projection * http://www.safe.com
