GPS geodetic ellipsoidal coordinates (latitude, longitude and height) are relative to an ellipsoid (WGS84). Computation of GPS height differences is not a true topographic levelling because GPS heights are relative to the ellipsoid surface (+ above or - below). Topographic levelling uses gravitic equipotential surfaces (the Geoid is one of this kind). The water flows (when not using water pumps) due to gravity. So for open channel water supply systems true levelling is almost mandatory.
Best regards Antonio 2012/10/25 andrea antonello <[email protected]> > Hi I need some information about the above subject. > > We are planning a educational project for water management networks in > Ethiopia and we applied to get a precision GPS to do the surveys. > > We just got hit by one very upset persons responsible for the project > that told us that a professor of topography explained them that: > "since in Africa there is not geoid, the GPS is useless" > > Apart of the citation, which may rise some comments on its own, I was > wondering if there is something I am not considering and should really > know. We have used gps in Rwanda without problems for the same > purposes and I am quite puzzled about what I am missing. > > Any advice or link to documentation is very appreciated, > Thanks, > Andrea > _______________________________________________ > This message is sent to you from [email protected] mailing list. > Visit http://lists.osgeo.org/mailman/listinfo/foss-gps to manage your > subscription > For more information, check http://wiki.osgeo.org/wiki/FOSS-GPS >
_______________________________________________ This message is sent to you from [email protected] mailing list. Visit http://lists.osgeo.org/mailman/listinfo/foss-gps to manage your subscription For more information, check http://wiki.osgeo.org/wiki/FOSS-GPS
