Georeferencing tiff by creating tfw file

[Ed McNierney]

Dejan -

The gdalinfo utility is telling you the pixel size.  The fourth line of
the output below, beginning with "Origin = ", ends with "Pixel Size = ".
Those are the very same values you would use in the first and fourth
lines, respectively, of a TFW file.  It looks like this is the same
value you calculated, and it appears to be correct.

	- Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
ed at topozone.com
(978) 251-4242  

-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
Behalf Of Gambin Dejan
Sent: Wednesday, November 16, 2005 8:59 AM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: [UMN_MAPSERVER-USERS] Georeferencing tiff by creating tfw file

Hi,

Even there are probably some utils I can use, I would still like to know
how can I calculate the "pixel size" parameter in tfw file (so the first
and fourth parameter) from the existing tiff file and the following
informations:

For example, "gdalinfo my.tif" says

Driver: GTiff/GeoTIFF
Size is 8857, 5905
Coordinate System is `'
Origin = (5455749.998925,5021000.001075) Pixel Size =
(0.00215084,-0.00215084)
Metadata:
  TIFFTAG_XRESOLUTION=300
  TIFFTAG_YRESOLUTION=300
  TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch) Corner Coordinates:
Upper Left  ( 5455749.999, 5021000.001)
Lower Left  ( 5455749.999, 5020987.300)
Upper Right ( 5455769.049, 5021000.001)
Lower Right ( 5455769.049, 5020987.300)
Center      ( 5455759.524, 5020993.651)
Band 1 Block=8857x5905 Type=Byte, ColorInterp=Palette
  Color Table (RGB with 2 entries)
    0: 255,255,255,255
    1: 0,0,0,255

I have xy coordinates (in meters): 5455750 and 5021000 and the scale of
25.40363554. I have tried using the simple formula like:

pixel size in inches = scale/resolution, so 25.40363554/300 and
converting it to meters gives me 0.002150841. But this is not correct,
right?

Wiht CAD overlay I have got 0.08467878514170, that is probably right...

What am I doing wrong? Is it the resolution that I am using? Do I have
to use screen resolution or what?

thanks 

regards, dejan