Hi,<br><br>I am trying to convert a gif map downloaded from <a href="http://aviationweather.gov/data/products/swl/ll_12_0_cl_new.gif">http://aviationweather.gov/data/products/swl/ll_12_0_cl_new.gif</a> to georeferenced tiff. I found out that the Projection used to create this GIF map is Polar Stereographic from the North Pole (90.0), center meridian 97W and height of 0.<br>
<br>Map corners:<br>Upper Left = 44.5 N 135 W <br>Lower Right = 19.9N 74W<br><br>I used cs2cs in FWTools-2.0.6 to obtain the points for -a_ullr in gdal_translate command:<br><br><i>cs2cs +proj=latlon +to +proj=stere +lat_0=90 +lon_0=-97 -r <<EOF >pts_stere_xy.dat<br>
+44.5 135.0W <br>+19.9 74.0W<br>EOF</i><br><br>Points created:<br><i> cat pts_stere_xy.dat<br>-3297702.30 -4220866.46 0.00<br>3492766.64 -8228442.54 0.00</i><br><br>Then I used gdal_translate to create the geotiff image:<br>
<i>ulx=-3297702.30<br>uly=-4220866.46<br>lrx=3492766.64<br>lry=-8228442.54<br><br>gdal_translate -of GTiff -co PROFILE=GEOTIFF -co INTERLEAVE=PIXEL -a_srs '+proj=stere +lat_0=90 +lon_0=-97' -a_ullr $ulx $uly $lrx $lry ../maps/my_image.gif ../maps/my_image_sterePts.tif</i><br>
<br><br><br>geotiff image information:<br><i>Driver: GTiff/GeoTIFF<br>Files: my_image_sterePts.tif<br>Size is 864, 526<br>Coordinate System is:<br>PROJCS["unnamed",<br> GEOGCS["WGS 84",<br> DATUM["unknown",<br>
SPHEROID["unnamed",6378137,298.2572235629972]],<br> PRIMEM["Greenwich",0],<br> UNIT["degree",0.0174532925199433]],<br> PROJECTION["Polar_Stereographic"],<br>
PARAMETER["latitude_of_origin",90],<br> PARAMETER["central_meridian",-97],<br> PARAMETER["scale_factor",1],<br> PARAMETER["false_easting",0],<br> PARAMETER["false_northing",0],<br>
UNIT["metre",1,<br> AUTHORITY["EPSG","9001"]]]<br>Origin = (-3297702.299999999813735,-4220866.459999999962747)<br>Pixel Size = (7859.339050925926131,-7618.965931558935154)<br>Metadata:<br>
AREA_OR_POINT=Area<br>Image Structure Metadata:<br> INTERLEAVE=BAND<br>Corner Coordinates:<br>Upper Left (-3297702.300,-4220866.460) (135d 0'0.00"W, 44d30'0.00"N)<br>Lower Left (-3297702.300,-8228442.540) (118d50'21.73"W, 20d21'8.25"N)<br>
Upper Right ( 3492766.640,-4220866.460) ( 57d23'32.09"W, 43d34'2.00"N)<br>Lower Right ( 3492766.640,-8228442.540) ( 74d 0'0.00"W, 19d54'0.00"N)<br>Center ( 97532.170,-6224654.500) ( 96d 6'8.37"W, 38d 0'27.51"N)<br>
Band 1 Block=864x9 Type=Byte, ColorInterp=Palette<br> Color Table (RGB with 256 entries)<br> 0: 0,0,0,255<br>....... color table continues .....</i><br><br><br><b>Q1: Could someone let me know if the commands I used look OK?</b><br>
I am able to display the image using openev, however I cannot display it using another proprietary software. <br>I am no expert so, I may be using the tools incorrectly or something of the like. <br><br><b>Q2: Does the image info show anything seriously wrong I don't see?</b><br>
<br><b>Q3: Any suggestion on how to perform the conversion differently?</b><br><br>Thanks<br>