.. [#fnogcsrid] *See id.* at Ch. 2.3.8, p. 39 (Geometry Values and Spatial Reference Systems).
.. [#fnsrid] Typically, SRID integer corresponds to an EPSG (`European Petroleum Survey Group <http://www.epsg.org>`_) identifier. However, it may also be associated with custom projections defined in spatial database's spatial reference systems table.
.. [#fnharvard] Harvard Graduate School of Design, `An Overview of Geodesy and Geographic Referencing Systems <http://www.gsd.harvard.edu/gis/manual/projections/fundamentals/>`_. This is an excellent resource for an overview of principles relating to geographic and Cartesian coordinate systems.
.. [#fnthematic] Terry A. Slocum, Robert B. McMaster, Fritz C. Kessler, & Hugh H. Howard, *Thematic Cartography and Geographic Visualization* (Prentice Hall, 2nd edition), at Ch. 7.1.3.
.. [#fndist] This limitation does not apply to PostGIS.
.. [#fngeography] Please refer to the `PostGIS Geography Type <http://postgis.net/docs/manual-2.1/using_postgis_dbmanagement.html#PostGIS_Geography>`_ documentation for more details.