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accessInformation:
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Information & Knowledge Management Dept., Geospatial Section, 1st Floor, Keller House, 121 Loop Street, Cape Town. Contact: Ms. Lara Röttcher, Tel. 021 487 2599, email: lara.rottcher@capetown.gov.za. Data distributed by City Maps public counter, 7th Floor, Keller House, 121 Loop Street, Cape Town. |
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description:
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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. |