non-square shapefiles and tileindex

[Ara.T.Howard]

On Mon, 5 Feb 2007, Frank Warmerdam wrote:

> OK, with the data package you provided, I was able to reproduce the problem.
> In fact, all the orbits were being drawn, but the OFFSITE wasn't working as
> desired so nodata was being written over valid data.

wow!  thanks for the speedy delivery!

> There are two problems.
>
> The first is that OFFSITE is completely ignored for greyscale input data.  I
> believe I omitted this because it seemed to me that the OFFSITE ought to
> apply to the input pixel value, but that was difficult since OFFSITE is an
> RGB tuple.

ah.  i actually tried

   OFFSITE 255

for exactly that reason.  i thought it might work ;-)

>
> The second problem is that OFFSITE processing is applied *after* any scaling
> or other processing.
>
> As it turns out the greyscale processing does try to honour known nodata
> values marked in the metadata of the source raster.  So you can either add
> it in the .hdr files (I don't think GDAL supports this for ENVI files) or
> you can provide an override in the map file as a processing statement.
>
> eg.
>  PROCESSING "NODATA=255"
>
> However, it turns out that NODATA testing is applied *after* scaling as well
> due to the way processing in MapServer works.  This is clearly not what you
> would desire, and it in fact gets reported as an issue in the debug stream
> if you have debug on.  By by careful selection of your scaling in your case
> you can ensure that only the 255 values end up mapping to 255 in the final
> result.  To do that I slightly altered your scaling to:
>
>  PROCESSING "SCALE=0,64"
>  PROCESSING "NODATA=255"
>
> Thus any value of 64 or higher is mapped to 255, and values from 0-63 are
> mapped to 0 to 254 or so.  This gives the desired output.
>

hmmm.  i made those edits to the mapfile, which you can see here

   http://www.ngdc.noaa.gov/eog/maps/public/dmsp/F15/2007/02/01/demo/mapfile

then i ran this shp2img command

   shp2img -m index.map -i png -o a.png -e -180 -30 180 30 -l vis -all_debug 42

which was successful and created this

   http://www.ngdc.noaa.gov/eog/maps/public/dmsp/F15/2007/02/01/demo/a.png

progress!

however, this is still not quite right.  you can see in this loop

   http://www.ngdc.noaa.gov/eog/maps/public/dmsp/F15/2007/02/01/demo/data/F1520070203.loop.gif

that the roi is, in fact, covered on that western edge.

i'm at a loss as to how that command could 'partially' work.  is that the
result you got?  or was the entire longitudal range covered?

also very strange, is that requests for individual orbits sometime work and
sometimes do not

   http://www.ngdc.noaa.gov/eog/maps/public/dmsp/F15/2007/02/01/demo/orbits.html

try the second one:

   http://www.ngdc.noaa.gov/eog/maps/public/dmsp/F15/2007/02/01/demo/?SERVICE=WCS&REQUEST=GetCoverage&Coverage=F15200702030145.nt.d.OIS.vis&CRS=EPSG:4326&BBOX=-180,-10,180,10&Format=png

this file definitely contains data

   http://www.ngdc.noaa.gov/eog/maps/public/dmsp/F15/2007/02/01/demo/data/F15200702030145.nt.d.OIS.vis.png

in fact, all of them do.

i tried commenting out the OFFSITE sections of those layers with no luck - so
some of them display totally blank.

> I have filed the following bug report with regard to OFFSITE values.  I
> believe that OFFSITE values ought to be supported for greyscale inputs, and
> they should be interpreted in terms of the output RGB tuple that would be
> produced.

great!

>  http://mapserver.gis.umn.edu/bugs/show_bug.cgi?id=2024
>
> BTW, in MapServer 5.0 the new RFC 21 color correction allows easier
> non-linear color correction on the fly.  In your case the following
> produces better results than the simple linear scaling:
>
>  PROCESSING "LUT=0:0,20:128,63:254"
>
> If you are bold, you might consider upgrading to MapServer 5 (aka development
> version) and experiment with that.

i'm bold.  but government sysads tend to be slightly less so where the
internet is concerned.  ;-(  thanks for the tip though.

cheers.

-a
-- 
we can deny everything, except that we have the possibility of being better.
simply reflect on that.
- the dalai lama