The CUAHSI Conference on Hydroinformatics
Workshop: Use GDAL, PKTOOLS and GRASS for massive raster operations in hydrology
Giuseppe Amatulli, Yale University
Geospatial Data Abstraction Library (GDAL), Processing Kernel for geospatial data (PKTOOLS) and Geographic Resources Analysis Support System (GRASS) are powerful command line utilities that are essential for manipulating and analyzing large geo-datasets. In the context of hydrological modelling, they can be used for data pre-processing but also to extract hydrographic features (stream network, flow accumulation, flow direction etc.) from digital elevation models. In the first part of the workshop, I will explain the main principles behind these tools by illustrating examples of simple geodata processing for raster cropping and re-projection, image masking, spatial and temporal/spectral filtering. I will also explain how to maximize computational operations and process raster data more efficiently by building routines that allow the saving of temporary raster outputs in RAM and using VRT files for tiling operations in a multicore environment. In the second part of the workshop, I will demonstrate how to correctly start a GRASS session and how to automate common geo-data processing tasks. In the context of hydrological modelling, I will use the MERIT-DEM to predict flow direction, stream network extraction and basin delineation. I will also teach how to compute geomorphology features, such as profile and tangential curvature, first and second order derivatives and geomorphology classes. Basic command line knowledge (any language is fine) and general know-how of geospatial data processing and hydrological modelling are prerequisites for this workshop. Participants should bring laptops with 25GB free on their hard disk, which will be used to install a customized OSGeo-Live virtual machine with GDAL and PKTOOLS and GRASS included.