"Feinberg, Harold" wrote: > If you are running MI 6.5 the process is automatic if your .tfw is in the > same directory as your tiff file. In other words, when you select open file > and select your raster image MI 6.5 will first ask if you want to register > the image, click register, then you will be prompted for the projection of > your image and your image given it's own fully georeferenced .tab file. > Kudos to MI 6.5 development team for this addition. If are running 6.0 or > earlier you could download the tfwread utility on the directions site.
Hi All! Not in my MI 6.5. It simply asks for at least three reference points when I try to follow the advice above. For you who succeeds, better check one thing. I tried the tfwread utility which simply takes the numbers from the tfw file and transfers those to a proper raster tab file. This approach disregards an important difference between the tfw specification and a tab file for raster image registration. A tfw file georeferences the CENTER of the top left pixel and then calculates all other pixel coordinates by adding as pixelnumber times pixelsize (a rotation may be be specified as well) A MapInfo tab file georeferences a number (at least three) of pixels, freely distributed across the image. I always like to define at least the four corners if I have an orthophoto or similar raster image. But MapInfo georeferences the TOP LEFT CORNER of the pixel in question. If this is not taken into account, it will mean a shift by half a pixel size when a tfw is converted to a tab. Also, the tfwread utility only calculates the coordinates for the top left three pixels. That is no better control than the tfw file offers. A better solution would be to calculate the expected coordinate values for the four corners of the image, shifting half a pixel in x and y and then writing a tab file on those points. Regards, Mats.E -- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: :Email/ [EMAIL PROTECTED] ICQ#9517386 : :---------------------------------------------------------------------: :Mail/ GISKRAFT, Mats Elfstroem, Vaepplingv 21, SE-227 38 LUND, SWEDEN: :Phones: +46 46 145959, +46 70 595 3935 : ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: _______________________________________________________________________ List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MapInfo-L" in the message body.
