[Freegis-list] TFW format

[Petr]

ok, i know that my map is in S-42 coordinate system. what else i need to know to convert GPS 
coordinate to position in bitmap?

Thnak you

Bill Thoen wrote:
> On Thu, Oct 06, 2005 at 04:12:01PM +0200, Petr wrote:
> 
>>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.
> 
> 
> Googling on "tfw format" I found the following on
> http://www.asmail.be/msg0055111818.html:
> ---
> A sample TFW file opened up would look like:
> 
>                 +6.00
>                 -0.00
>                 -0.00
>                 -6.00
>                 1709053.00
>                 807714.00
> 
>         Line 1 - Cell size in the "X" direction
>         Line 2 - Insertion point in the "X" direction
>         Line 3 - Insertion point in the "Y" direction
>         Line 4 - Cell size in the "Y" direction
>         Line 5 - Easting value of insertion point "X"
>         Line 6 - Northing value of insertion point "Y"
> 
> Note that sign on line 4 will tell you if the insertion point is the upper
> left or lower left corner.  A positive means the "Y" values are increasing
> upwards and therefore, the registration must be starting at the bottom or
> lower corner. Vice-versa for a negative sign.
> ---
> 
> Also, the GeoTIFF format spec can be found at:
> http://www.remotesensing.org/geotiff/spec/geotiffhome.html
> 
> 
> 
>>I need transform standard GPS coordinate (eg.: 50d04m55sN 14d26m03sE) to 
>>pixel coordinate in my map (eg.: 256px,414px aproximately) and backwards.
> 
> 
> Unfortunately, knowing the TFW format won't help you with converting your
> GPS coordinate. The TFW file doesn't contain coordinate system information,
> so you don't know the projection method, datum, etc.  But once you convert
> it into the same system used in your TIFF file, the tfw parameters can be
> used to locate it on your image accurately. 
>  
> - Bill Thoen