table provides information about available spatial reference
systems for spatial data. This table is based on the SQL/MM
(ISO/IEC 13249-3) standard.
Entries in the
are based on the European Petroleum
Survey Group (EPSG) data set, except for SRID 0, which
corresponds to a special SRS used in MySQL that represents an
infinite flat Cartesian plane with no units assigned to its axes.
For additional information about SRSs, see
Section 11.4.5, “Spatial Reference System Support”.
table has these columns:
The spatial reference system name. This value is unique.
The spatial reference system numeric ID. This value is unique.
SRS_IDvalues represent the same kind of values passed as the SRID argument to spatial functions. SRID 0 (the unitless Cartesian plane) is special. It is always a legal spatial reference system ID and can be used in any computations on spatial data that depend on SRID values.
The name of the organization that defined the coordinate system on which the spatial reference system is based.
The numeric ID given to the spatial reference system by the organization that defined it.
SRS definition parsing occurs on demand when definitions are needed by GIS functions. Parsed definitions are cached in the data dictionary cache so that parsing overhead is not incurred for every statement that needs SRS information.
The spatial reference system description.
DESCRIPTIONcolumns contain information that may be of interest to users, but they are not used by MySQL.
mysql> SELECT * FROM ST_SPATIAL_REFERENCE_SYSTEMS WHERE SRS_ID = 4326\G *************************** 1. row *************************** SRS_NAME: WGS 84 SRS_ID: 4326 ORGANIZATION: EPSG ORGANIZATION_COORDSYS_ID: 4326 DEFINITION: GEOGCS["WGS 84",DATUM["World Geodetic System 1984", SPHEROID["WGS 84",6378137,298.257223563, AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]], PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]], UNIT["degree",0.017453292519943278, AUTHORITY["EPSG","9122"]], AXIS["Lat",NORTH],AXIS["Long",EAST], AUTHORITY["EPSG","4326"]] DESCRIPTION:
This entry describes the SRS used for GPS systems. It has a name
SRS_NAME) of WGS 84 and an ID
SRS_ID) of 4326, which is the ID used by the
European Petroleum Survey
DEFINITION values for projected and
geographic SRSs begin with
GEOGCS, respectively. The definition for SRID 0
is special and has an empty
The following query determines how many entries in the
correspond to projected, geographic, and other SRSs, based on
mysql> SELECT COUNT(*), CASE LEFT(DEFINITION, 6) WHEN 'PROJCS' THEN 'Projected' WHEN 'GEOGCS' THEN 'Geographic' ELSE 'Other' END AS SRS_TYPE FROM ST_SPATIAL_REFERENCE_SYSTEMS GROUP BY SRS_TYPE; +----------+------------+ | COUNT(*) | SRS_TYPE | +----------+------------+ | 1 | Other | | 4668 | Projected | | 483 | Geographic | +----------+------------+
To enable manipulation of SRS entries stored in the data dictionary, MySQL provides these SQL statements:
CREATE SPATIAL REFERENCE SYSTEM: See Section 13.1.19, “CREATE SPATIAL REFERENCE SYSTEM Statement”. The description for this statement includes additional information about SRS components.