Contents
- 1 Which is the latest version of PostGIS for SQL?
- 2 What is the spatial ref SYS table in PostGIS?
- 3 When do you need a SRID in PostGIS?
- 4 When to use dynamic SQL in PostgreSQL 33.5?
- 5 Which is the best way to express an object in OpenGIS?
- 6 Is the PostGIS extended format superset of OGC?
- 7 Which is the basis for the PostGIS geographic type?
Which is the latest version of PostGIS for SQL?
As of version 0.9, PostGIS supports all the objects and functions specified in the OGC “Simple Features for SQL” specification. PostGIS extends the standard with support for 3DZ,3DM and 4D coordinates. 4.1.1. OpenGIS WKB and WKT
What is the spatial ref SYS table in PostGIS?
The spatial_ref_sys table is a PostGIS included and OGC compliant database table that lists over 3000 known spatial reference systems and details needed to transform/reproject between them.
What are the GIS objects supported by PostGIS?
The GIS objects supported by PostGIS are a superset of the “Simple Features” defined by the OpenGIS Consortium (OGC). As of version 0.9, PostGIS supports all the objects and functions specified in the OGC “Simple Features for SQL” specification. PostGIS extends the standard with support for 3DZ,3DM and 4D coordinates. 4.1.1.
When do you need a SRID in PostGIS?
The SRID is required when creating spatial objects for insertion into the database. Input/Output of these formats are available using the following interfaces: bytea WKB = ST_AsBinary(geometry); text WKT = ST_AsText(geometry); geometry = ST_GeomFromWKB(bytea WKB, SRID); geometry = ST_GeometryFromText(text WKT, SRID);
As of version 0.9, PostGIS supports all the objects and functions specified in the OGC “Simple Features for SQL” specification. PostGIS extends the standard with support for 3DZ,3DM and 4D coordinates. 4.1.1. OpenGIS WKB and WKT
The GIS objects supported by PostGIS are a superset of the “Simple Features” defined by the OpenGIS Consortium (OGC). As of version 0.9, PostGIS supports all the objects and functions specified in the OGC “Simple Features for SQL” specification. PostGIS extends the standard with support for 3DZ,3DM and 4D coordinates. 4.1.1.
When to use dynamic SQL in PostgreSQL 33.5?
33.5. Dynamic SQL In many cases, the particular SQL statements that an application has to execute are known at the time the application is written. In some cases, however, the SQL statements are composed at run time or provided by an external source.
How to execute an arbitrary statement in PostgreSQL?
The simplest way to execute an arbitrary SQL statement is to use the command EXECUTE IMMEDIATE. For example: EXEC SQL BEGIN DECLARE SECTION; const char *stmt = “CREATE TABLE test1 (…);”; EXEC SQL END DECLARE SECTION; EXEC SQL EXECUTE IMMEDIATE :stmt;
Which is the best way to express an object in OpenGIS?
The OpenGIS specification defines two standard ways of expressing spatial objects: the Well-Known Text (WKT) form and the Well-Known Binary (WKB) form. Both WKT and WKB include information about the type of the object and the coordinates which form the object.
Is the PostGIS extended format superset of OGC?
PostGIS extended formats are currently superset of OGC one (every valid WKB/WKT is a valid EWKB/EWKT) but this might vary in the future, specifically if OGC comes out with a new format conflicting with our extensions. Thus you SHOULD NOT rely on this feature!
How is a gist index used in PostGIS?
GiST (Generalized Search Trees) indexes break up data into “things to one side”, “things which overlap”, “things which are inside” and can be used on a wide range of data-types, including GIS data. PostGIS uses an R-Tree index implemented on top of GiST to index GIS data.
Which is the basis for the PostGIS geographic type?
The basis for the PostGIS geographic type is a sphere. The shortest path between two points on the sphere is a great circle arc. That means that calculations on geographies (areas, distances, lengths, intersections, etc) must be calculated on the sphere, using more complicated mathematics.