New 25cm Aerial Photos available from Chief Directorate: National Geo-spatial Information (CD:NGI)

It was recently announced on the OSGeo Africa mailing list that CD:NGI is hoping to have complete 25cm Ground Sample Distance (GSD) Ortho-Rectified aerial imagery coverage of South Africa by the end of March 2023.

Previously myself, @Adrian_Frith, @Gerhardus_Geldenhuis and others have collected copies/updates of the 50cm aerial imagery from CD:NGI in Cape Town. I have previously mostly been responsible for processing and hosting it.

The 25cm Imagery is 12TB and is made up of around 45000 GeoTIFF 280MB files.

The imagery will likely need to be reprojected to Web Mercator projection, tiled and overviews generated to be usable in JOSM, iD and other OpenStreetMap editors.

Most likely the source imagery will be converted to Cloud Optimized GeoTIFF with embedded overviews and served using TiTiler’s MosaicJSON support but this still needs to be finalised. @Adrian_Frith has previously used this method for NGI’s 1:50k topographic maps, but there may be scaling issues when running this against the significantly larger 25cm imagery dataset.

At the moment we are not sure where the imagery will be processed and what will be used for the final hosting. The OpenStreetMap Foundation do have a Dev server, but this “only” has 14TB of available storage.


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