[gdal-dev] Converting from Lambert (LCC) to latlong/mercator

[Brian Murray]

>From the gdal_translate line, the images are identical, but with added
information to the tif, in a geotif style.

Once I warp it, the image is squished (as I would expect), but the
width is the same.

I have also tried embedding all of the geotiff data within the
intermediate image, but for some reason, I just cannot seem to set the
pixel size. If I create a wld or a tfw file, it just seems to ignore
it.

gdal_translate -of gtiff -CO TFW=YES -a_ullr -115 56 -105 54 -a_srs
"+proj=lcc +lat_0=56 +lon_0=-115 +lat_2=49.33 +lat_1=54.66 +x_0=0
+y_0=0 +datum=NAD27" n.tif nn.tif

I am wondering if perhaps its because photoshop added a bunch of
incorrect meta data:

Metadata:
  AREA_OR_POINT=Area
  TIFFTAG_SOFTWARE=Adobe Photoshop CS3 Macintosh
  TIFFTAG_DATETIME=2009:02:21 16:15:49
  TIFFTAG_XRESOLUTION=72
  TIFFTAG_YRESOLUTION=72
  TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch)

To my eyes, that looks like 72pixels per inch, which is about right
for the scanner it came in from, but wrong for the actual map scale. I
cannot find a way in photoshop to change that, and it definitely
doesn't like scaling to sizes below 1.0

On Sat, Feb 21, 2009 at 8:45 PM, Wendy Fay Stevenson <stevensw at erau.edu> wrote:
> Hi
>
> Have you not got a world file for your image?
> I would agree that the pixel size does not seem right.  I
> would try writing my own world file with reasonable values -
> just to see if the image come out looking better.  Make sure
> you call it the same name as your original tiff file (with
> .wld or .twf extention) and gdal will automatically pick it
> up.
>
> What results do you get if you run gdalinfo on the new file?
> Does it have more or less the same number of pixels?
>
> I know you can set the resolution with gdalwarp but I haven't
> tried that.
>
> About the false eastings and northings, it would very much
> depend on the projection of the original image.  If they do
> not specify I would assume they are 0.
>
> Wendy
>