AWARE SYSTEMS
TIFF and LibTiff Mail List Archive

Thread

1999.09.10 14:45 ".tfw format", by Mario Boratto
1999.09.11 06:01 "Re: .tfw format", by James McMullen
1999.09.13 15:22 "RE: .tfw format", by Geoff Vandegrift

1999.09.11 06:01 "Re: .tfw format", by James McMullen

This is surprisingly obscure information, considering how widely used
TFW is.

A web search turned up only a dead link into ESRI; no doubt the official
definition is there somewhere. AFAIK, TFW says nothing about units or
projection; you just have to know that a particular file is, say, NAD27
California State Plane Zone 6.

The following is from the good folks at ER Mapper, with whom I have no
affiliation:

Q34. Can ER Mapper use TIFF World files (TFW)?"

A. The TFW file was created to give spatial location to the massive
amounts of
        imagery that is traded around in TIFF, which does not carry any
coordinate
        information on it's own.

In a directory structure, the TFW file will have the same name as the TIFF

it is referencing as in this example:

                image_x.tif
                image_x.tfw

The TFW structure is extemely simple. It is a 6 line file that can be

opened up and read in any text editor such as WordPad or Notepad in Windows.

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.

--
http://www.cityROM.com

james@iimap.com