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The `-ot` switch can be used to alter the output data type.
Use gdalinfo to verify data type.
Rescaling
The `-outsize` switch can be used to set the size of the output file.
Use gdalinfo to verify the size.
The `-scale` switch can be used to rescale data. Explicit control of the input and output ranges is also available. The gdalinfo `-mm` switch can be used to see pixel min/max values.
Let's split our image into two with `-srcwin` which makes a copy based on pixel/line location (xoff yoff xsize ysize). You also could use `-projwin` and define the corners in georeferenced coordinates (ulx uly lrx lry).
Raster tileindex with gdaltindex
You can build a shapefile as a raster tileindex. For every image a polygon is generated with the bounds of the extent of the polygon and the path to the file.
Have a look at your output shapefile with QGIS and ogrinfo (you will learn more about ogrinfo later in this tutorial)
Reprojecting
For this process we assume that HYP_50M_SR_W.tif has been properly created with bounds. As we saw before with gdainfo no coordinate system was set. So we assign WGS84 as coordinate system to the image in the first step.
The gdalwarp command can be used to reproject images. Here we reproject the WGS84 geographic image to the Mercator projection:
Use gdalinfo to verify the change and have a look at the image.
Here we reproject to the Ortho projection.
Note how the poles are clipped? This is because the edges at the pole can't be reprojected gdalwarp does not read all the data. We can force gdalwarp to read a bunch of surplus data around chunks as one way to resolve this.
Note how the poles are clipped? This is because the edges at the pole can't be reprojected gdalwarp does not read all the data. We can force gdalwarp to read a bunch of surplus data around chunks as one way to resolve this. Read more about this in the RasterTutorial https://trac.osgeo.org/gdal/wiki/UserDocs/RasterProcTutorial.
Mosaicking
gdal_merge.py is a python script that can be used for simple mosaicking tasks. Mosaic the east.tif and west.tif into a single file:
The same task can be accomplished with gdalwarp. gdalwarp has a variety of advantages over gdal_merge, but can be slow to merge many files:
Get to know OGR
Open the shape file with a Desktop GIS like QGIS, and have a look.
Get information about the vector data with ogrinfo
Get a summary about your data with ogrinfo together with `-so`.
If you run ogrinfo without a parameter you will get a summary about your data and afterwards a section for every dataset.
You can forward the result from ogrinfo to grep to filter and get only the attribute COUNTRY.
You can convert your data to other formats. Get the list of the supported formats with `--formats`.
Use ogr2ogr to convert data between file formats
You can use ogr2ogr to converts simple features data between file formats. You can use `--formats` to get the list of the supported formats with read/write information.
Convert the countries to GML.
Things to try
Here are some additional challenges for you to try:

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  2. gdal_quickstart
  3. English
Note how the poles are clipped? This is because the edges at the pole can't be reprojected gdalwarp does not read all the data. We can force gdalwarp to read a bunch of surplus data around chunks as one way to resolve this. Read more about this in the RasterTutorial https://trac.osgeo.org/gdal/wiki/UserDocs/RasterProcTutorial.
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