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PostGIS - Geographic Information Systems Extensions to PostgreSQL ~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ VERSION: 1.0.0 (2005/01/13) MORE INFORMATION: http://postgis.refractions.net INTRODUCTION: This distribution contains a module which implements GIS simple features, ties the features to rtree indexing, and provides some spatial functions for accessing and analyzing geographic data. Directory structure: ./ Build scripts and install directions. ./lwgeom Library source code. ./jdbc Extensions to the PostgreSQL JDBC drivers to support the GIS objects. ./doc Documentation on the code, objects and functions provided. ./loader A program to convert ESRI Shape files into SQL text suitable for uploading into a PostGIS/PostgreSQL database and a program for converting PostGIS spatial tables into Shape files.. ./examples Small programs which demonstrate ways of accessing GIS data. INSTALLATION: PostGIS is compatible with PostgreSQL 7.2 and above. To install the module, move this directory to the "contrib" directory of your PostgreSQL source installation. Alternately, point PGSQL_SRC at your PostgreSQL source tree either in an environment variable or editing Makefile.config. You *must* have a PostgreSQL source tree, and you *must* have succesfully built and installed it for this to work. SEE THE NOTE ON GEOS SUPPORT BELOW FOR SPECIAL COMPILATION INSTRUCTIONS * PROJ4 SUPPORT (Recommended): The Proj4 reprojection library is required if you want to use the transform() function to reproject features within the database. http://www.remotesensing.org/proj Install Proj4 in the default location. Edit the postgis Makefile.config and change the USE_PROJ variable to 1 and ensure that the PROJ_DIR variable points to your Proj4 installation location (/usr/local is the default). * SPATIAL PREDICATE / GEOS SUPPORT (Recommended): The GEOS library provides support for exact topological tests such as Touches(), Contains(), Disjoint() and spatial operations such as Intersection(), Union() and Buffer(). http://geos.refractions.net In order to use the GEOS support, you *may* need to specially compile your version of PostgreSQL to link the C++ runtime library. To do this, invoke the PgSQL configuration script this way: LDFLAGS=-lstdc++ ./configure --your-options-go-here The initial LDFLAGS variable is passed through to the Makefile and adds the C++ library to the linking stage. Once you have compiled PgSQL with C++ support, you can enable GEOS support in PostGIS by setting the USE_GEOS variable in the PostGIS Makefile.config to 1, and ensure that the GEOS_DIR variable points to your GEOS installation location (/usr/local is the default). To compile PostGIS, as root run: make make install PostGIS now requires the PL/pgSQL procedural language in order to operate correctly. To install PL/pgSQL use the 'createlang' program from the PostgreSQL installation. (The PostgreSQL Programmer's Guide has details if you want to this manually for some reason.) As postgres run: createlang plpgsql yourdatabase psql -f lwpostgis.sql -d yourdatabase Installation should now be complete. UPGRADING: Upgrading PostGIS can be tricky, because the underlying C libraries which support the object types and geometries may have changed between versions. To avoid problems when upgrading, you will have to dump all the tables in your database, destroy the database, create a new one, add the PL/pgSQL language, upload the new postgis.sql file, then upload your database dump: pg_dump -t "*" -f dumpfile.sql yourdatabase dropdb yourdatabase createdb yourdatabase createlang plpgsql yourdatabase psql -f lwpostgis.sql -d yourdatabase psql -f dumpfile.sql -d yourdatabase vacuumdb -z yourdatabase You might find the utils/postgis_restore.pl useful. It will automatically create a new db, feed it the lwpostgis.sql file and restore all but postgis objects from a 'custom' dump. Run with no args to have a usage string printed. USAGE: Try the following example SQL statements to create non-OpenGIS tables and geometries: CREATE TABLE geom_test ( gid int4, geom geometry,name varchar(25) ); INSERT INTO geom_test ( gid, geom, name ) VALUES ( 1, 'POLYGON((0 0 0,0 5 0,5 5 0,5 0 0,0 0 0))', '3D Square'); INSERT INTO geom_test ( gid, geom, name ) VALUES ( 2, 'LINESTRING(1 1 1,5 5 5,7 7 5)', '3D Line' ); INSERT INTO geom_test ( gid, geom, name ) VALUES ( 3, 'MULTIPOINT(3 4,8 9)', '2D Aggregate Point' ); SELECT * from geom_test WHERE geom && 'BOX3D(2 2 0,3 3 0)'::box3d; The following SQL creates proper OpenGIS entries in the SPATIAL_REF_SYS and GEOMETRY_COLUMNS tables, and ensures that all geometries are created with an SRID. INSERT INTO SPATIAL_REF_SYS ( SRID, AUTH_NAME, AUTH_SRID, SRTEXT ) VALUES ( 1, 'EPSG', 4269, 'GEOGCS["NAD83", DATUM[ "North_American_Datum_1983", SPHEROID[ "GRS 1980", 6378137, 298.257222101 ] ], PRIMEM["Greenwich",0], UNIT["degree",0.0174532925199433]]' ); CREATE TABLE geotest ( id INT4, name VARCHAR(32) ); SELECT AddGeometryColumn('db','geotest','geopoint',1,'POINT',2); INSERT INTO geotest (id, name, geopoint) VALUES (1, 'Olympia', GeometryFromText('POINT(-122.90 46.97)',1)); INSERT INTO geotest (id, name, geopoint) VALUES (2, 'Renton', GeometryFromText('POINT(-122.22 47.50)',1)); SELECT name,AsText(geopoint) FROM geotest; Spatial Indexes: PostgreSQL provides support for GiST spatial indexing. The GiST scheme offers indexing even on large objects, using a system of "lossy" indexing where a large object is proxied by a smaller one in the index. In the case of the PostGIS indexing system, all objects are proxied in the index by their bounding boxes. You can build a GiST index with: CREATE INDEX <indexname> ON <tablename> USING GIST ( <geometryfield> ); Always run the "VACUUM ANALYZE <tablename>" on your tables after creating an index. This gathers statistics which the query planner uses to optimize index usage.