Hi Frank, I had a look to the raster-howto and the sources as well, but was unsure, because I can't imagine that most users have grids that exactly have values between 0 and 255 in it. So sorry fot the questions. Do you plan to implement a colormap for ascii grids like the clr for binary grids? What would you suggest to display the negative values?
Thanks, Carola > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Frank Warmerdam > Sent: Monday, January 16, 2006 7:29 AM > To: Carola Jesch > Cc: [email protected] > Subject: Re: [UMN_MAPSERVER-USERS] negative values and colors > in Ascii Grids > > On 1/15/06, Carola Jesch <[EMAIL PROTECTED]> wrote: > > Hi, > > > > I have an contineous ASCII GRID (floating values) that I > would like to > > display in MapServer. This grid shows bathymetry (ocean) > and elevation > > (land) data. There are a lot of negative values for the ocean, > > starting from -1500 to 0 and only a small range for the land (0 to > > 20). When I am trying to display the grid, the entire image > is black. > > Does MapServer support negative values? How can I display > the grid with colors? > > I have tried to convert the Ascii file to a binary grid, > but I don't > > know how to create a colormap (*.clr). ArcGIS doesn't seem > to support > > this or does anyone of you how to do that? > > Carola, > > By default Mapserver will read the grid values directly, and > clip any values outside the range 0 to 255 the bounds. So > all your negative values are cliipped to zero, and the top > value is 20 (out of 255) which would appear nearly black. > > The first step I would suggest is enabling autoscaling with > the layer directive: > > PROCESSING "SCALE=AUTO" > > Beyond that I would suggest you review the raster howto. > > http://mapserver.gis.umn.edu/docs/howto/raster_data > > Best regards, > -- > ---------------------------------------+---------------------- > ---------- > ---------------------------------------+------ > I set the clouds in motion - turn up | Frank Warmerdam, > [EMAIL PROTECTED] > light and sound - activate the windows | http://pobox.com/~warmerdam > and watch the world go round - Rush | Geospatial > Programmer for Rent >
