[Freegis-list] TFW format

Frank Warmerdam warmerdam at pobox.com
Thu Oct 6 16:28:29 CEST 2005

On 10/6/05, Petr <freegis at pbox.cz> wrote:
> Hello,
> i need help with tfw format. I have tiff image and tfw file with description:
> 200.00000000
> 0.00000000
> 0.00000000
> -200.00000000
> 3408200.0000
> 5635500.0000
> I searched internet and not found any information about using of this map.
> I need transform standard GPS coordinate (eg.: 50d04m55sN 14d26m03sE) to pixel coordinate in my map
>   (eg.: 256px,414px aproximately) and backwards.


You need to determine what coordinate system your image is using.  It
is clearly some sort of projected coordinate system.  Till you know
that, the .tfw isn't going to do you much good.

By the way, the .tfw is saying that the center of the top left pixel
of the image is at (3408200,5635500) and that each pixel is
200x200 (likely 200 meters by 200 meters).

But without the coordinate system, you can't relate that to latitude
and longitude values.

Once you do have the coordinate system, you can use the PROJ.4
(or another projections package) to convert between lat/long values
and projected coordinates.  Then use the .tfw values to turn the
projected values into pixel/line locations.

BTW, do you happen to have a .prj file too?

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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