I figured out the problem. Well, at least how to fix it. After playing with it some more, I determined that mapserver wasn't treating the data set as 8-bit signed, but instead was treating it as 8-bit unsigned. I converted it to 16-bit signed, and it worked great.
Chris > -----Original Message----- > From: UMN MapServer Users List > [mailto:[EMAIL PROTECTED] On Behalf Of Chris Garrard > Sent: Monday, May 08, 2006 10:17 AM > To: [email protected] > Subject: Re: [UMN_MAPSERVER-USERS] displaying rasters with > negative pixel values > > Hi Chris, > > Thanks for looking at this. Here's the map file. It displays classes > c5 - c10 just fine, and shows part of the data from the c4 class. I > have big blank areas for classes c1 - c3. If I use either of the > commented-out processing directives instead of the classes, I > still get > the blank areas. The image displays fine in other software, so I know > the data are there. > > MAP > NAME utah > EXTENT -1510000 -285000 -1020000 375000 > UNITS METERS > IMAGETYPE png > SIZE 450 450 > > OUTPUTFORMAT > NAME PNG > DRIVER "GD/PNG" > MIMETYPE "image/png" > IMAGEMODE RGBA > EXTENSION "png" > TRANSPARENT OFF > END > > WEB > IMAGEPATH "/webgis/apache/htdocs/tmp/" > IMAGEURL "/tmp/" > END > > LAYER > NAME mintemp > TYPE raster > STATUS default > DATA '/auto/earth2/ars_data/statedata/utah/ut_tmin.img' > # PROCESSING "SCALE=AUTO" > # PROCESSING "SCALE=-7,10" > CLASS > NAME 'c1' > TITLE '(-7) - (-6)' > EXPRESSION ([pixel] >= -7 AND [pixel] <= -6) > COLOR 0 0 255 > END > CLASS > NAME 'c2' > TITLE '(-5.9) - (-4)' > EXPRESSION ([pixel] > -6 AND [pixel] <= -4) > COLOR 54 97 255 > END > CLASS > NAME 'c3' > TITLE '(-3.9) - (-2)' > EXPRESSION ([pixel] > -4 AND [pixel] <= -2) > COLOR 56 171 255 > END > CLASS > NAME 'c4' > TITLE '(-1.9) - 0' > EXPRESSION ([pixel] > -2 AND [pixel] <= 0) > COLOR 0 255 255 > END > CLASS > NAME 'c5' > TITLE '0 - 1' > EXPRESSION ([pixel] > 0 AND [pixel] <= 1) > COLOR 145 255 181 > END > CLASS > NAME 'c6' > TITLE '1.01 - 2' > EXPRESSION ([pixel] > 1 AND [pixel] <= 2) > COLOR 209 255 105 > END > CLASS > NAME 'c7' > TITLE '2.01 - 3' > EXPRESSION ([pixel] > 2 AND [pixel] <= 3) > COLOR 255 255 0 > END > CLASS > NAME 'c8' > TITLE '3.01 - 4' > EXPRESSION ([pixel] > 3 AND [pixel] <= 4) > COLOR 255 184 0 > END > CLASS > NAME 'c9' > TITLE '4.01 - 6' > EXPRESSION ([pixel] > 4 AND [pixel] <= 6) > COLOR 255 112 0 > END > CLASS > NAME 'c10' > TITLE '6.01 - 10' > EXPRESSION ([pixel] > 6 AND [pixel] <= 10) > COLOR 255 0 0 > END > END > > END > > > -----Original Message----- > > From: Christopher Condit [mailto:[EMAIL PROTECTED] > > Sent: Friday, May 05, 2006 5:59 PM > > To: Chris Garrard; [email protected] > > Subject: RE: [UMN_MAPSERVER-USERS] displaying rasters with > > negative pixel values > > > > Hi Chris- > > Can you send your map file? I've had great success with > > negative raster > > values when defining my own classes (Sea temperature GeoTIFF > > / AAI Grid, > > for instance). > > > > -Chris > > > > -----Original Message----- > > From: UMN MapServer Users List > > [mailto:[EMAIL PROTECTED] On > > Behalf Of Chris Garrard > > Sent: Friday, May 05, 2006 5:16 PM > > To: [email protected] > > Subject: [UMN_MAPSERVER-USERS] displaying rasters with > negative pixel > > values > > > > Hi all, > > > > I have a raster data set that has values from -7 to 10 (mean minimum > > temps C). I can't get any of the pixels with values less than -1 to > > display in mapserver. I have tried using the processing > directive to > > scale the values and I've tried specifying classes, and > neither works. > > I have also tried different file formats (geotiffs and erdas .img). > > > > Anyone know why this isn't working? > > > > I'm using mapserver 4.8.3 and gdal 1.3.1 on solaris 10. > > > > Thanks for any ideas, > > Chris > > >
