[Proj] Lambert projection with one or two standard parallels and proj4

[Charles Karney]

The default values of lat_1 and lat_2 are 33 and 45, so in your first
example you had +lat_1=46.244 +lat_2=45 which is not what you intended.
The second example does what you wanted.

   --Charles

On 04/25/2013 03:51 AM, Linton Corbet wrote:
> Hello all,
>
> I'm sure there is a gap in my understanding, but I haven't been able to
> identify where it is, nor how to fill it. My issue is this:
>
> I'm transforming lon lat coordinates into a lambert conformal conic
> projection.
>
> The lambert projection uses a single standard parallel 46.244 and the
> central meridian is 17.0. And it's on a sphere, but that's not
> particularly relevant here. I am using packages that use the proj4 library.
>
> I test the transformation using linux tool cs2cs as follows:
>
> echo "15.220483 48.437298" | cs2cs +proj=lonlat +to +proj=lcc
> +lat_1=46.244 +lat_0=46.244 +lon_0=17. +a=6367470 +b=6367470
> +ellps=sphere +datum=WGS84
>
> -131346.80 245318.16
>
> I also understand that the one-standard parallel form is the same as the
> two-standard parallel form if the two standard parallels are the same.
> It is more convenient for me to give all parallels in my scripts - let
> proj do the work. So I also test with:
>
> echo "15.220483 48.437298" | cs2cs +proj=lonlat +to +proj=lcc
> +lat_1=46.244 +lat_2=46.244 +lat_0=46.244 +lon_0=17. +a=6367470
> +b=6367470 +ellps=sphere +datum=WGS84
>
> -131290.66 245281.34
>
> yet I get different results. Any ideas as to why?
>
> And at very least, what am I doing wrong and which approach should I use?
>
> Kind regards,
> Linton Corbet
>
>
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