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25.28 The INFORMATION_SCHEMA ST_SPATIAL_REFERENCE_SYSTEMS Table

Table des matières

The ST_SPATIAL_REFERENCE_SYSTEMS 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 ST_SPATIAL_REFERENCE_SYSTEMS table 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 11.5.5, “Spatial Reference System Support”.

The ST_SPATIAL_REFERENCE_SYSTEMS table has these columns:

  • SRS_NAME

    The spatial reference system name. This value is unique.

  • SRS_ID

    The spatial reference system numeric ID. This value is unique.

    SRS_ID values 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.

  • ORGANIZATION

    The name of the organization that defined the coordinate system on which the spatial reference system is based.

  • ORGANIZATION_COORDSYS_ID

    The numeric ID given to the spatial reference system by the organization that defined it.

  • DEFINITION

    The spatial reference system definition. DEFINITION values are WKT values, represented as specified in the Open Geospatial Consortium document OGC 12-063r5.

    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.

  • DESCRIPTION

    The spatial reference system description.

Notes

  • The SRS_NAME, ORGANIZATION, ORGANIZATION_COORDSYS_ID, and DESCRIPTION columns contain information that may be of interest to users, but they are not used by MySQL.

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Example

  1. mysql> SELECT * FROM ST_SPATIAL_REFERENCE_SYSTEMS
  2.        WHERE SRS_ID = 4326\G
  3. *************************** 1. row ***************************
  4.                 SRS_NAME: WGS 84
  5.                   SRS_ID: 4326
  6.             ORGANIZATION: EPSG
  7. ORGANIZATION_COORDSYS_ID: 4326
  8.               DEFINITION: GEOGCS["WGS 84",DATUM["World Geodetic System 1984",
  9.                           SPHEROID["WGS 84",6378137,298.257223563,
  10.                           AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]],
  11.                           PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],
  12.                           UNIT["degree",0.017453292519943278,
  13.                           AUTHORITY["EPSG","9122"]],
  14.                           AXIS["Lat",NORTH],AXIS["Long",EAST],
  15.                           AUTHORITY["EPSG","4326"]]
  16.              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 Group (EPSG).

The DEFINITION values for projected and geographic SRSs begin with PROJCS and GEOGCS, respectively. The definition for SRID 0 is special and has an empty DEFINITION value. The following query determines how many entries in the ST_SPATIAL_REFERENCE_SYSTEMS table correspond to projected, geographic, and other SRSs, based on DEFINITION values:

  1. mysql> SELECT
  2.          COUNT(*),
  3.          CASE LEFT(DEFINITION, 6)
  4.            WHEN 'PROJCS' THEN 'Projected'
  5.            WHEN 'GEOGCS' THEN 'Geographic'
  6.            ELSE 'Other'
  7.          END AS SRS_TYPE
  8.        FROM ST_SPATIAL_REFERENCE_SYSTEMS
  9.        GROUP BY SRS_TYPE;
  10. +----------+------------+
  11. | COUNT(*) | SRS_TYPE   |
  12. +----------+------------+
  13. |        1 | Other      |
  14. |     4668 | Projected  |
  15. |      483 | Geographic |
  16. +----------+------------+

To enable manipulation of SRS entries stored in the data dictionary, MySQL provides these SQL statements:


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Document créé le 26/06/2006, dernière modification le 26/10/2018
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