The source SDTS dataset must be in the user's current directory. The files that make up the dataset are listed in the dataset's Catalog/Directory file (CATD); this file is specified by the user with the catd parameter.
v.in.sdts creates maps in your current mapset, and will only import map data if there is correspondence between the current mapset's coordinate system and that of the transfer set; in addition, for UTM (and State Plane), Zone designations must match. These specifications can be displayed be running v.in.sdts in "Information only" mode. "Information only" mode is automatically put in effect when there is a mis-match between source and target coordinate systems.
An SDTS dataset may consist of one or several distinct map layers (or "2-D manifolds", in SDTS terminology), coinciding with one or more partitions of the earth's surface. If a dataset contains more than one map layer, the grouping of object data into individual map layers, and of groups of map layers, is specified in the Catalog/Spatial Domain (CATS) file, in terms of "domain", "map", "theme", and/or "manifold" ("aggregate object"). If available, this information is displayed to the user in "Information Only" mode. The user can then either
SDTS and the Topological Vector Profile define two basic types of spatial objects: simple spatial objects, i.e., lines, polygons, nodes, etc.; and composite objects, which are made up of one or more other simple and/or composite spatial objects. SDTS composite objects, which GRASS cannot handle directly, are imported as records in RDBMS-ready tables. Details on the mapping of simple and composite spatial objects between SDTS and GRASS may be found in the GRASS-SDTS User Guide.
Only a brief explanation of SDTS attributes and v.in.sdts's handling of them is given here. See the GRASS/SDTS User Guide for details.
SDTS is capable of substantial attribute complexity. SDTS distinguishes between two basic kinds of attributes: primary attributes are related directly to spatial objects (simple or composite), while secondary attributes are related to primary or to other secondary attributes. In SDTS, attributes are stored in relational tables, and spatial objects may be linked to multiple attributes in one or more different attribute tables. The schema of an SDTS dataset--the number and kind of attribute fields and attribute tables, and the relationships among attributes and objects--is not predefined by the Standard or the Profile, but is determined by the producer of the dataset.
For most kinds of data likely to be available through SDTS, optimal access requires use of GRASS with a relational database management system. In support of this, v.in.sdts imports SDTS attribute tables in a form ready for use with your RDBMS. It also produces SQL-compatible scripts to set up the relational database and install the data.
dig_att and dig_cats files: The program does generate dig_att and dig_cats files, and for relatively simple SDTS datasets, i.e., those with one-to-one object-attribute relationships with all object attributes in a single attribute table, an associated relational database is not necessary. In addition, for more complex datasets, the dig_att and dig_cats files are constructed in such a way as to facilitate post-import incorporation of selected data from the attribute files for use without recourse to a relational database. Specifically, the contents of the generated dig_att and dig_cats files are as follows:
FID | obj_code | attr_code | attr. field 1 |...| attr. field n |(obj_code and attr_code are codes, derived from record IDs in the SDTS dataset, which function as keys in the import relational database. See The GRASS-SDTS User Guide for details.)
For other datasets, the dig_cats file is identical in content to the generated GRASS-database object link table, and records would have the structure:
FID | obj_code or FID | obj_code | attr_code
Full discussion of this topic may be found in the GRASS-SDTS User Guide.
vector map name: if the SDTS dataset contains a single map layer, or if a a single map layer from a multiple-map dataset, the name specified in output is used as is. Otherwise, the name is extended with integers to specify the individual layers. relational database file names: see the GRASS-SDTS User Guide.
m.sdts.read, v.in.sdts, v.out.sdts, v.sdts.dp.cp, v.sdts.meta.cp, v.sdts.meta