Aerial Photography Grid 5 Km X 5 Km

The 5km x 5km aerial photography grid is based on the 10km x 10km aerial photography grid. The 5km x 5km aerial photography grid was developed in the 1980s by the old Regional Services Council. Its practical use is to provide a unique number for each tile of 5km x 5km aerial (ortho) photography when dealing with aerial contractors and for planning purposes. Furthermore, it can be used as a useful reference guide to identify area's of interest for other geospatial work. The rectangular grid intersection co-ordinates are in Gauss Conform using positive Westings and Southings. The top right corner origin falls on the Lo19 Meridian and is at y = 0 and x = 3 700 000. Each 10km x 10km geocell (see CCT 10km x 10km Grid) is divided into four 5km x 5km cells, named A, B, C, D. The reference for each 10km x 10km geocell is derived from the top right corner and is made up of two digits – the first being the first digit of the y value and the second being the third digit of the x value. For example the geocell with a top right hand corner value y = + 30 000 and x = + 3 740 000 would have a reference of 34. In addition the letter W is added in front if the cell is located west of the Lo19 Meridian and the letter E is added if located east of the Lo19 Meridian.The 5km x 5km grid numbers are as follows: W00A, W00B, W00C, W00D, W10A, W10B, W10C, W10D, W20A… One row of cells is added to the east of the Lo19 Meridian: E00A, E00C, E01A, E01C, E02A, E02C….One row of geocells in the south has duplicate numbers going beyond x = 3 800 000. For example: Y = 50 000 and x = 3 700 000 gives W50B (North)Y = 50 000 and x = 3 800 000 gives W50B (South)Therefore, duplicate 10km x 10km tiles have been suffixed with a N for tiles lying in the north or S for for tiles lying in the south. In this case, W50N_B and W50S_B. All spatial layers are served live from internal systems, an item's "Last Updated" or "Publish Date" refers to the Metadata only.本5km×5km航空摄影网格基于10km×10km航空摄影网格构建。该5km×5km航空摄影网格由旧区域服务委员会（Regional Services Council）于20世纪80年代开发。其实际用途为：在对接航空承包商及开展规划工作时，为每一块5km×5km航空（正射）摄影（ortho）瓦片分配唯一编号。此外，该网格还可作为实用参考指南，用于识别其他地理空间工作的感兴趣区域。该矩形网格的交点坐标采用以西向坐标、南向坐标为正方向的高斯正形（Gauss Conform）坐标系。网格的右上角原点位于Lo19子午线处，对应坐标为y=0、x=3 700 000。每一个10km×10km地理单元（geocell，详见CCT 10km×10km网格）被划分为4个5km×5km子单元，分别命名为A、B、C、D。每个10km×10km地理单元的编号由其右上角坐标推导而来，由两位数字组成：第一位为y值的首位数字，第二位为x值的第三位数字。例如，右上角坐标为y=+30 000、x=+3 740 000的地理单元，其编号为34。此外，若单元位于Lo19子午线以西，则在编号前添加字母W；若位于以东，则添加字母E。5km×5km网格的编号示例如下：W00A、W00B、W00C、W00D、W10A、W10B、W10C、W10D、W20A……Lo19子午线东侧新增了一行子单元：E00A、E00C、E01A、E01C、E02A、E02C……南部存在一行地理单元，当x坐标超过3 800 000时会出现编号重复的情况。例如：y=50 000、x=3 700 000对应W50B（北侧）；y=50 000、x=3 800 000对应W50B（南侧）。因此，对于重复的10km×10km瓦片，北侧瓦片添加后缀N，南侧瓦片添加后缀S，此时编号为W50N_B和W50S_B。所有空间图层均从内部系统实时提供，要素的"Last Updated"或"Publish Date"仅指元数据（Metadata）的相关信息。