[FOSS-GPS] GPS issues for Ethiopia
andrea.antonello at gmail.com
Thu Oct 25 05:18:18 PDT 2012
thanks for the reply,
> 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.
I agree with this. Even if here we are talking about pressurized
pipes, a quite precise elevation is necessary.
The idea is to do some relative measurement for the vertical component.
But I should really not have any issue with the horizontal positions.
> Best regards
> 2012/10/25 andrea antonello <andrea.antonello at gmail.com>
>> 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,
>> This message is sent to you from FOSS-GPS at lists.osgeo.org mailing list.
>> Visit http://lists.osgeo.org/mailman/listinfo/foss-gps to manage your
>> For more information, check http://wiki.osgeo.org/wiki/FOSS-GPS
> This message is sent to you from FOSS-GPS at lists.osgeo.org mailing list.
> Visit http://lists.osgeo.org/mailman/listinfo/foss-gps to manage your
> For more information, check http://wiki.osgeo.org/wiki/FOSS-GPS
More information about the FOSS-GPS