====== Geotricks ======

This page is dedicated to sparse and casual tricks with some common GFOSS tools.

===== Merging multiple Geotiff bands =====

This command works with relatively recent [[http://gdal.osgeo.org/|Gdal]] versions:

<code>
gdal_merge.py -o multiband.tif -separate band1.tif band2.tif band3.tif
</code>

===== Changing raster resolution in Grass  =====

Just use the builtin computing region facility, it will use a nearest neighbor interpolation for this purpose:

<code>
g.region rast=original_map -p
g.region res=<new>
r.mapcalc "new_map=original_map"
</code>

A similar trick can be used to cut a portion of the original map, apply a mask, etc. A more capable module for those applications is ''r.resamp.interp'' which can be used instead of ''r.mapcalc'' to peform also bilinear and bicubic interpolation for the assigned raster grid. A nearest neighbor interpolation can also be performed by the ''r.resample'' module as well.

===== WMS/WFS at PCN =====

See [[WMS at PCN|here]] for details about using GRASS with national service at PCN.

===== Precision grid =====

[[http://lists.maptools.org/pipermail/proj/2011-April/005628.html|This]] is a very interesting thread about creating proj NTv2 precision grids starting from national precision grids in other formats, up to about 1:2000 scale and more.