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4 GRASS Project database

In the GRASS database spatially-oriented data are managed geocoded. For this purpose a coordinate system (e.g.: Gauß-Krüger, UTM, etc.) of the project region, the so called Location, needs to be decided upon before starting to work. Consider the following: As a rule, it is indispensable to choose the structure and organization of the database to be used in GRASS and each GIS.

Extent of the project region: All the data that are to be imported as part of a project must be contained within the spatial extent of the the Location. In addition one must determine what projection is to be used for the project. This is usually provided with the data to be used in the project and includes information about the projection such as projection name, ellipsoid, datum, and other parameters.

Data resolution of raster data: In general, the computing and storage requirements increase exponentially with resolution. However, if the resolution is lower than that of the dataset, there will be data loss and the resulting GIS will be less than satisfactory. Therefore, it is useful to choose the standard resoultion (default) to be equal to the resolution of the most important data layers. The raster resolution can always be adjusted once the region has been created. When importing data, the original resolution and map size is preserved.

Now that the properties of the project region and the data resolution have been determined, the next step is to create a subdirectory for the GRASS database. This is usually called 'grassdata' (see chapter 2.3).