R: [Proj] cs2cs usage

[Markus Neteler]

On Thu, Mar 20, 2008 at 3:22 PM,  <marco.pasetti at alice.it> wrote:
...
> then I entered the WGS84 point: 10°44'09,70E 45°45'12.00N as
>
> 10.73602778 45.75333333

You can also use this to do that transformation:

cs2cs -f "%.8f" +proj=latlong +datum=WGS84 \
      +to +proj=latlong +datum=WGS84
10d44'9.7"E 45d45'12"N

...
> 1635050.62      5068127.39 -45.30

I get the same result with my script here.


> now further questions:
>
> 1) what does "-45.30" mean?

You are changing the ellipsoid during this transformation.
So height will differ (-45.30meters less).


> 2) I roughly checked the point on my GRASS-imported rasters (imported in the
> location created by GRASS using EPSG code 3003 and the previously mentioned
> towgs84 parameters), and it seems to "be" where I expected... but I cannot
> be sure! I know the region, and I *have* some conspicuous points to *use*
> (it's on lake garda, and there's a peak nearby the point of interest that is
> clearly visible from the raster map), but this procedure is fairly long to
> be called a *secure and precise check procedure* (that's why I used the word
> *roughly*)

You need measured test points. I don't know if there are public test
points available for Italy...

Best,
Markus