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From: Ivan Shmakov on 25 Jan 2010 16:16
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Drawn by my quest for bizzare Shell scripts, I've written the
one that produces an image file using the nadir BRDF-adjusted
spectral reflectances derived from the MODIS sensors data (as
featured on the NASA EOS Terra and Aqua satellites.)

The script (below) will produce the image in the sinusoidal
projection, mainly due to the lack of magic, but also since the
MODIS data used is distributed that way. Also note that the
data is collected for ``land'' pixels only.

The script expects the HDF files to be in the current directory,
and sends the resulting image to stdout.

I've tested the script using a whole directory (1.66 GiB) of
MODIS data from [1], but it's designed to behave sensibly when
given a part of the data. With little tweaking, I expect this
script to be able to handle other MODIS L3 (say, NDVI, or
LAI/FPAR, or aerosol) datasets just as well.

(BTW, feel free to tweak the `sparsex' and `sparsey' settings at
the top of the script. The less the value the larger will be
the image. But note that setting both to 1 will result in a
43200x21600 PPM file, with the estimated size of 5.21 GiB.)

The results of the test run (converted to PNG) are at [2].
There's also an image further enhanced by $ convert -gamma 1.6
-modulate 130,120,100 at [3].

[1] ftp://e4ftl01u.ecs.nasa.gov/MODIS_Composites/MOTA/MCD43B4.005/2009.06.02/
[2] http://waterlily.siamics.net/~ivan/graphic/1264450492.png
[3] http://waterlily.siamics.net/~ivan/graphic/1264450492-1.png
[4] http://en.wikipedia.org/wiki/MODIS
[5] http://en.wikipedia.org/wiki/Earth_Observing_System
[6] http://en.wikipedia.org/wiki/Sinusoidal_projection
[7] http://en.wikipedia.org/wiki/Hierarchical_Data_Format
[8] http://en.wikipedia.org/wiki/NetCDF

#!/bin/bash
### mcd43b4-globe-1.sh --- Global Aqua+Terra MODIS (MCD43B4) mosaic -*- Sh -*-

## NB: comment out for big-endian (MSB first) systems
le=-littleendian
varp=Nadir_Reflectance_Band
tilew=1200 ; tileh=1200
sparsex=40 ; sparsey=40
tw=$(($tilew / $sparsex)) ; th=$(($tileh / $sparsey))
iw=$((36 * $tw)) ; ih=$((18 * $th))
rawtopgmopts="-bpp 2 ${le} -maxval 15999 ${tw} ${th}"
ix="$(seq 0 "$sparsex" 1199)" ; iy="$(seq 0 "$sparsey" 1199)"
p=/tmp/$(date +%s).${RANDOM}.
i1="$p"1.ppm ; i2="$p"2.ppm ; i3="$p"3.ppm ; it="$p"t.ppm
: > "$i1"
for v in $(seq -f %02.f 0 17) ; do
: > "$i2"
for h in $(seq -f %02.f 0 35) ; do
for f in MCD43B4.A???????."h${h}v${v}".005.?????????????.hdf ; do
if ! [ -e "$f" ] ; then
ppmmake rgb:0/0/0 "$tw" "$th"
else
rgb3toppm <(ncget-hdf --raw -- "$f" "$varp"{1,4,3} \
"${iy}, ${ix}" \
| rawtopgm $rawtopgmopts)
fi
break
done > "$i3"
if ! [ -s "$i2" ] ; then
mv -- "$i3" "$i2"
else
pnmcat -leftright "$i2" "$i3" > "$it"
mv -- "$it" "$i2"
fi
done
if ! [ -s "$i1" ] ; then
mv -- "$i2" "$i1"
else
pnmcat -topbottom "$i1" "$i2" > "$it"
mv -- "$it" "$i1"
fi
done
rm -- "$i2" "$i3"

## .
exec cat -- "$i1"

### mcd43b4-globe-1.sh ends here

- --
FSF associate member #7257
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