qdgc Israel

QDGC tables delivered in geopackage file
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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.

Within each geopackage file you will find a number of tables with these names:
-tbl_qdgc_01
-tbl_qdgc_02
-tbl_qdgc_03
-tbl_qdgc_04
-tbl_qdgc_05
-etc

The attributes for each table are:
qdgc Unique Quarter Degree Grid Cell reference string
area_reference Country
level_qdgc QDGC level
cellsize degrees decimal degree for the longitudal and latitudal length of the cell
lon_center Longitude center of the cell
lat_center Latitudal center of the cell
area_km2 Calculated area for the cell
geom Geometry

Metadata
--------
Geodata GCS_WGS_1984
Datum: D_WGS_1984
Prime Meridian: 0

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:
- st_area(st_transform(geom, 102022))/1000000)

Conditions
----------
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

Thankyou
--------
The work has over the years been supported and received advice and moral support from many organisations and stakeholders. Here are some of them:
- Tanzania Wildlife Research Institute
- Dept of Biology, NTNU, Norway
- Norwegian Environment Agency
- Eivin Røskaft, Steven Prager, Howard Frederick, Julian Blanc, Honori Maliti, Paul Ramsey

References
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* 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

以GeoPackage文件交付的QDGC数据表
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四分之一度网格单元格（Quarter Degree Grid Cell，QDGC）是一种通过覆盖特定区域的近似等面积正方形，来表征该区域特定属性的制图方法。此类正方形基于覆盖全球的经纬度方格：赤道附近共有360条经线，南北极之间共有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GeoPackage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：唯一四分之一度网格单元格引用字符串
area_reference：所属国家/地区
level_qdgc：QDGC层级
cellsize：单元格经向与纬向长度，单位为十进制度
lon_center：单元格中心经度
lat_center：单元格中心纬度
area_km2：计算得到的单元格面积，单位为平方千米
geom：几何图形

元数据
--------
地理坐标系统：GCS_WGS_1984
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完成。以非洲大陆为例，使用非洲阿尔伯斯等面积圆锥投影的计算语句如下：
- st_area(st_transform(geom, 102022))/1000000

使用条款
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本数据集按现状交付，不提供任何明示或默示的担保。若发现数据错误，请告知作者，我将尽力修正。改进建议可提交至以下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、建议与精神鼓励，以下为部分致谢对象：
- 坦桑尼亚野生动物研究所
- 挪威科技大学生物学系
- 挪威环境局
- Eivin Røskaft、Steven Prager、Howard Frederick、Julian Blanc、Honori Maliti、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