Hi, you work with georeferenced data and not with images. Therefor you have to declare in the tfw-file the coordinate of the left upper pixel in the correct projection. It could be that the gdal-tools have a program to cut an georeferenced image into georeferenced tiles. Mit freundlichen Grüssen
Arnd Wippermann http://gis.ibbeck.de/ginfo/ _____ Von: UMN MapServer Users List [mailto:[EMAIL PROTECTED] Im Auftrag von Ian Gesendet: Mittwoch, 23. Januar 2008 20:27 An: [email protected] Betreff: [UMN_MAPSERVER-USERS] Tiff world file question SRTM3 data (.img format w/index) for a basemap is slow, so to speed up our draw times I'm using a script to make smaller tiles of this data. My script writes the images to .tif format and works, but I also need to generate tiff world files to maintain spatial reference. The definition I found for the .tfw format is: First row is x-pixel resolution Second and third rows are "rotational components" but are set to zero in the case of an unrotated map. The fourth row is the y-pixel resolution. The negative sign indicates that the image y-axis is positive down which is the opposite from real world coordinates. The 5th and 6th rows are the Easting and Northing of the upper left pixel (0,0 in image coordinates) So for SRTM3 data which is 90m resolution I am creating a .tfw file like: 90.00 0.00 0.00 -90.00 ??? ??? The last two rows are confusing me. Do I need to calculate the pixel position of the upper left corner of each new tile with respect to the pixels of ALL SRTM3 files? That calculation could be problematic. Also if there is another tiling solution that maintains spatial reference I'm all ears. Thank you.
