[Proj] Proj4js, cs2cs and pj_transform

[nicolas david]

Hi

pj_transform use lat/long coordinate in radian. So you have to convert them
to degree with  "RAD_TO_DEG "  defined at the value  57.29577951308232 in
proj_api.h

Nicolas

2011/12/7 Cyril Bondue <c.bondue at hotmail.com>

>  Hello fellow coders!
>
> I'm writing to ask for your help. I need to convert data from NTF (Paris)
> / Lambert Centre France (epsg 27562) to WGS84 (epsg 4326). To test Proj4 I
> used the web interface Proj4js, and i could do the conversion without much
> troubles. Here are the two projPj I used, and working :
>  - source : +proj=lcc +lat_1=46.8 +lat_0=46.8 +lon_0=0 +k_0=0.99987742
> +x_0=600000 +y_0=200000 +a=6378249.2 +b=6356515
> +towgs84=-168,-60,320,0,0,0,0 +pm=paris +units=m +no_defs
>  - dest : +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs
> Good! But I need to do the conversion in a C++ program, so I downloaded
> the source, downloaded the NAD for France (who were already in the archive
> BTW), compiled with MinGW (i'm doing a Windows software), compilation runs
> without problems, great!
>
> Now, troubles ^^
> Here is my code :
>
> projPJ source = pj_init_plus("+proj=lcc +lat_1=46.8 +lat_0=46.8 +lon_0=0
> +k_0=0.99987742 +x_0=600000 +y_0=200000 +a=6378249.2 +b=6356515
> +towgs84=-168,-60,320,0,0,0,0 +pm=paris +units=m +no_defs");
> projPJ dest = pj_init_plus("+proj=longlat +ellps=WGS84 +datum=WGS84
> +no_defs");
>
> double x = 535003.285368d;
> double y = 200358.358412d;
> pj_transform(source, dest, 1, 1, &x, &y, NULL);
>
> pj_transform returns 0 (OK), but x and y are wrong. I have x=0.0259181 and
> y=0.816814 while the correct results are 1.485 and 46.8 (rounded up),
> results that Proj4Js confirms.
> I also tried the same transformation on cs2cs :
> cs2cs.exe +proj=lcc +lat_1=46.8 +lat_0=46.8 +lon_0=0 +k_0=0.99987742
> +x_0=600000 +y_0=200000 +a=6378249.2 +b=6356 515
> +towgs84=-168,-60,320,0,0,0,0 +pm=paris +units=m +no_defs +to +proj=longlat
> +ellps=WGS84 +datum=WGS84 +no_defs
> 535003.285368 200358.358412
> Results are different and also wrong (or i can't read them right)
> x=1d29'6"E, y=46d48'N 44.005
>
> I have taken care of settings PROJ_LIB with the nad folder. So i must do
> something wrong, i've tried many things but i don't understand what
> happens, so here I am, asking you for some assistance. Can you see what's
> going on?
>
> Thank you in advance!
>
> Cyril
>
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