[Proj] Can I convert the ellipsoids using Proj?

Davide Cesari dcesari at arpa.emr.it
Wed Aug 20 03:18:45 EST 2014

On 20/08/2014 09:37, Cleo Drakos wrote:
> Dear Noel and Alain
> Thanks for your nice answers.
> So, while calling the cs2cs, where can I input the lat, lon and elevation?
> cs2cs -f %.9f +a=6378136.30 +rf=298.257 +proj=latlong +towgs84=0,0,0 +to
> +a=6378137 +rf=298.25722356 +proj=latlong +towgs84=0,0,0
> cleo

Dear Cleo,
	with the command line indicated above, lon lat and optional altitude 
should be provided in standard input, i.e. typed by keyboard; on linux 
and unix-like systems shell (and probably DOS command line as well), you 
can take standard input from a text file with the syntax:

cs2cs ... < filenamewithlonandlat

Alternatively, the cs2cs command can receive as an extra argument the 
name of a file containing the coordinates, I suggest you to experiment 
with all the variations. Notice that the order of the coordinate is lon 
lat, not lat lon, but there are switches to change this as well as other 
formal aspects of cs2cs behavior, please refer to the cs2cs/proj 

> On Wed, Aug 20, 2014 at 3:37 PM, Alain Orsoni <Alain.Orsoni at ign.fr
> <mailto:Alain.Orsoni at ign.fr>> wrote:
>     Cleo,
>     If I understand correctly you have latitude, longitude, elevation
>     (considered as heigth above ellipsoid) and geoid (considered as
>     height above geoid).
>     If so, you have to input only latitude longitude and elevation in
>     proj4. Heigth above geoid remains the same whatever the ellipsoid
>     you use, it is just the height of the geoid above the ellipsoid
>     which changes when you change ellipsoid.
>     The elevation above ellipsoid will change because of the change of
>     ellipsoid dimensions.

============================= Davide Cesari ============================
Dott**(0.5) Davide Cesari
ARPA-Emilia Romagna, Servizio IdroMeteoClima
NWP modelling - Modellistica numerica previsionale
Tel. +39 051525926

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