Determine what coordinate system to use

A first step in planning a project is to determine what coordinate system to use.

Before you begin

Before you create a coordinate system, your user ID must have DBADM authority on the database that has been enabled for spatial operations. No authorization is required to use an existing coordinate system.

About this task

After you enable a database for spatial operations, you are ready to plan projects that use spatial data. You can use a coordinate system that was shipped with Db2® Spatial Extender or one that was created by elsewhere. Over 2000 coordinate systems are shipped with Db2 Spatial Extender.

You can plant projects that use spatial data and use one of the 2,000 coordinate systems that are included with Db2 Spatial Extender or a custom one that was created by another users.

To find out more about these coordinate systems, and to determine what other coordinate systems were shipped are included with Db2 Spatial Extender, and what (if any) coordinate systems have been created by other users, consult the DB2SE.ST_COORDINATE_SYSTEMS catalog view.

Procedure

To determine what coordinate system to use:

  1. Review existing coordinate systems that are shipped are included with Db2 Spatial Extender and use the corresponding spatial reference system that is based on the coordinate system of your choice.
    The most used coordinate systems are:
    • GCS_NORTH_AMERICAN_1983. Use this coordinate system when you need to define locations in the United States; for example:
      • When you import spatial data for the United States from the Spatial Map Data available for download.
    • A coordinate system that Db2 Spatial Extender refers to as Unspecified. Use this coordinate system when:
      • You need to define locations that have no direct relationship to the earth's surface; for example, locations of offices within an office building or locations of shelves within a storage room.
      • You can define these locations in terms of positive coordinates that include few or no decimal values.
  2. If you cannot find an existing coordinate systems in Db2 Spatial Extender, you can create one using one of the following methodsas follows:
    • Issue the db2se create_cs command from the db2se command line processor.
    • Run an application that invokes the DB2SE.ST_CREATE_COORDSYS procedure.

    Creating a coordinate system is rarely necessary. You need to also create an spatial reference system based on the new coordinate system.