Apologies for this non-sundial question, but I do hope someone can help. I've always been under the impression that Latitude/Longitude is a universal and unambigious method of indicating a position on the earth but now I am not so sure....
In South-Africa, the National survey system is based on a Gauss conform system with the Clarke 1880 (Modified) Ellipsoid. It is fundamentaly the same as the wordwide UTM system, with a slightly different scale factor, and the width of a system is only two degrees in longitude, one on either side of a central meridian, whereas UTM covers six degrees. Now the National system is based on the the same projection but we are using the WGS 84 ellipsoid. That caused the Latitude of a fixed point to increase South by 2,04 arc seconds, and Longitude West by 1,06 arc seconds (approximately), and the projected co-ordinates changed by approx. 296 metres South and 27 metres West (Differences calculated by comparing coordinates from the old system with the new system, around Pretoria). I am under the impession that Lat/Long is astronomically fixed from distant objects, with the origin being the rotation axis of the earth, so how can the values be influenced by adopting a new ellipsoid ? What fundamentals am I missing? D. Anton Reynecke
