# [Proj] Re: To handle geographic info from HDF5 formated Satellite Data

Aydin agerturk at gmail.com
Thu May 8 09:51:49 EDT 2008

```Frank Warmerdam <warmerdam <at> pobox.com> writes:

>
> Aydin wrote:
> > Frank,
> >
> > Thank you for response.
> > if I use your suggestion, for example pixel (1000,1000);
> >
> > longitude = -25 + 0.560648 * 1000 = 5581.48
> > latitude = 75 - 0.560648 * 1000 = -5531.48
> >
> > So, it is not possible.
> >
> > I do not have problem converting projected space to geographic space using
> > proj lib. My problem is how can calculate the distance from the corner
using
> > below parameters than I can convert those to lat/lon.
>
> Aydin,
>
> I stand corrected - the pixel size turns out to be in km not decimal degrees.
>
> So you will have to offset from the top left corner using:
>
> x (easting) = -2782987.27 + 560.648 * pixel
> y (northing) = 8348961.81 - 560.648 * line
>
> Then reproject that point back to long/lat using
>
> proj -I +proj=eqc +lat_ts=0 +lon_0=0.000000 +ellps=WGS84
>
> Good luck,
Frank,

Thank you very much that you pay time for me.
Unfortunately, it does not work. Let me show.
We have centre lon/lat values which are: lon=9.719999, lat=50.47374
Centre point pixel value are XCenter=2250, Ycenter=1583.

x (2250) = -2783 + 2250*0.560648  = -1521.5 km.
y (1583) =  8349 - 1583*0.5621554 =  7459 km.

When get the lon/lat using proj
lon = -13.667867
lat =  67.006235

which are not true.

It is realy diffcult to solve this porblem at least for me.

Best regards,

Aydin

```