Docs: theJGrass workspace

Overview of a GRASS database structure:




Most important files and folders for now

• WIND - contains the active processing region and the resolution
• PROJ_INFO - contains the information about the projection
• PROJ_UNITS - contains the information about projection units used
• cell, fcell - contain the raster files
• vector - contain the vector data since GRASS 6
• sites_list - contain the sites type data, deprecated from GRASS 6 on, but maintained in JGrass

File structure of GRASS Location

A GRASS raster map consists of several files in several subdirectories in a mapset, organized as follows:

• cellhd/: map header including projection code, coordinates representing the spatial extent of the raster map, number of rows and columns, resolution, and information about map compression;
• cell/, fcell/ or grid3/: generic matrix of values in a compressed, portable format which depends on the raster data type (integer, floating point or 3D grid);
• hist/: history file which contains metadata such as the data source, the command that was used to generate the raster map, or other information provided by the user;
• cats/: optional category file which contains text or numeric labels assigned to the raster map categories;
• colr/: optional color table;
• cell_misc/: optional timestamp, range of values, quantization rules (for floating point maps) and null (no-data) files;

GRASS vector maps are stored in several separate files in a single directory. While the attributes are stored in either a DBF file, a SQLite file or in an external DBMS (PostgreSQL, MySQL, ODBC), the geometric data are saved as follows:

• head: vector map ASCII header with information about the map creation (date and name), its scale and threshold;
• coor: binary geometry file which includes the coordinates of graphic elements (primitives) that define the vector feature;
• topo: binary topology file describes the spatial relationships between the map's graphic elements;
• hist: history ASCII file with complete commands that were used to create the vector map, as well as the name and date/time of the map creation;
• cidx: binary category index file which is used to link the vector object IDs to the attribute table rows;
• dbln: ASCII file which contains definition(s) of link to attribute storage in database (DBMS).

Taken from the GRASS developer's manual