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Clipping raster layers is a basic operation in many GIS workflows. Since rasters often cover large spatial extents, it is often beneficial to extract (or clip) only the portion of the raster that pertains to a specific study area. This can greatly improve data load and rendering times and decrease the time needed for tools…
With GIS analysis it’s a common occurrence that multiple raster tiles are required to cover a study area. For many analyses, and specifically hydrological analyses, a seamless, single raster is needed. The solution for combining multiple raster layers is to perform a raster merge, also referred to as a raster mosaic. QGIS uses the the…
PyQGIS has some methods for accessing single values in a raster, but the best way to access raster data is using the Geospatial Data Abstraction Library, or GDAL. GDAL comes pre-installed on the QGIS Python interpreter, so if you access the Python interpreter from QGIS (Plugins > Python Console) you won’t have to install any…
Objectives: Get statistics for a raster band Open the QGIS Python Console From the menu, select Plugins -> Python Console, or Ctrl + Alt + P (Windows) You can type directly into the console, or select the pad and paper icon to write code in the editor. I prefer to write code in the editor…
Objectives: Query the value of a raster layer at a points Open the QGIS Python Console From the menu, select Plugins -> Python Console, or Ctrl + Alt + P (Windows) You can type directly into the console, or select the pad and paper icon to write code in the editor. I prefer to write…
List the data attributes Accessing the var property of our netCDF varialbe will list the data attributes for the netCDF file. The output shows us this dataset has one data attribute with the name ‘data’. Which is contained within the names property of var. Calling the names property directly after the attributes() call gives the same result. We can get the name of specific…
Let’s get right into the code. First, make sure you have the ncdf4 package installed. This requires the netcdf4 and hdf5 software to be installed. netcdf4 and hdf5 are not r packages. There are various sources for installing these on your machine. I found this guide to work well for Ubuntu. Once all dependencies are installed we can load…
