[Proj] cs2cs syntax help

[Hermann Peifer]

On 2013-10-24 6:46, Szilard Albert wrote:
> The task is to convert UTM Zone 53 XY coordinates into Lat/Lon
> coordinates, keeping datum.

For this task, you don't really need cs2cs. proj -I or invproj can be 
used. See below.

>
> I am using:
>
> *cs2cs -W2 +proj=utm +zone=53 +south  +datum=WGS84 +to  +proj=latlong
> +datum=WGS84
> 669734.6 7607027.2
> 136d38'24.07"E  21d37'54.60"S 0.000*
>
> getting a result that seems fine.
>
> However, the following issues arise:
>
> 1. My input data is on the GDA94 datum. When I try  +datum=GDA94 (or
> GDA), I get
> /<cs2cs>:
> projection initialization failure
> cause: unknown elliptical parameter name./

proj -ld (or cs2cs -ld) gives the list of known datums. GDA or GDA94 are 
not mentioned there. However, you do not have to worry, as you anyway 
want to keep the datum.

>
> Am I safe using WGS84, since the difference between these 2 datums is
> less than 1 m? (http://www.geoproject.com.au/gda.faq.html).
>
> 2. I have heaps of other parameters of my input data - as below - should
> any of these be incorporated in my command,
> or datum and zone are enough?
>
> Datum GDA94
> Spheroid GRS80
> Semi-major axis
> Projection UTM MGA Z 53
> Central meridian 135 E
> False E/N, Scale factor 0.9996 etc
>

I would simply use: invproj -W2 +proj=utm +zone=53 +south +ellps=GRS80

Other parameters like central meridian, scale factor, etc. do not need 
to be specified explicitly. They are implied through +proj=utm and +zone=53.


Hermann