[FOSS-GPS] GPS issues for Ethiopia

andrea antonello andrea.antonello at gmail.com
Fri Oct 26 05:11:14 PDT 2012

Dear Iulio,

>> We are planning a educational project for water management
>> networks in
>> Ethiopia
> Good luck for your project, especially because it is educational.

Thank you!

> You said do not have a precise vertical network, even so you can use GPS and mix it with traditional topographic leveling for critical nstallations.
> I do not know your project extension and precision requirements but i believe you can use GPS and a relative geoid undulation to correct the geometric height differences and get an almost orthometric height.
> I have used EGM2008 and  this way and get realy good results.
> Pay attention on EGM2008 if you have no gravitational anomalies in your working area and for sure this simple differential model will give you acceptable results.
> Hj - Hi = (hj - hi) - ( Nj - Ni )
> H=orthometric
> h=geometric
> N=geoid ondulation
> http://www.fig.net/pub/athens/papers/ts07/ts07_8_roman.pdf

Thanks you, since we are talking about small networks, I think we
should really get good results, I appreciate you backup my guess.

I will read throught the documentation, thanks!

Best regards,

> best regards,
> julio menezes
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