Create a New Geographic Coordinate System

Feature Description

The Coordinate System Settings dialog box supports creating a new geographic coordinate system.

Feature Entry

  • Start tab -> Data Processing group -> Projection Settings -> Projection Settings window -> New Coordinate System -> Geographic Coordinate System.
  • Workspace Manager dataset context menu -> Properties -> Coordinate System option -> Reset Coordinate System... -> Projection Settings window -> New Coordinate System -> Geographic Coordinate System.
  • Map context menu -> Properties -> Layer Properties panel -> Coordinate System option -> Reset Coordinate System... -> Projection Settings window -> New Coordinate System -> Geographic Coordinate System button.

Steps

  1. In the Coordinate System Settings dialog box, click the New Coordinate System drop-down button and select Geographic Coordinate System to open the Custom Geographic Coordinate System dialog box.
  2. In the Custom Geographic Coordinate System dialog box, configure the following parameters:
    • Name: Specifies the name of the custom geographic coordinate system.
    • Datum: A datum defines the position of the Earth's spheroid relative to the Earth's center, providing a reference framework for geodetic measurements and establishing the origin and orientation of latitude/longitude lines. Each country/region has its own datum. Common datums in China include: Beijing 1954 and Xian 1980.
      • Predefined Datum: Click the drop-down button to select a predefined datum type. When using system-provided datums, the reference spheroid and parameters (semi-major axis/flattening) become fixed and uneditable.
      • Custom Datum: Enter a new name in the text box to create a custom datum, allowing modification of reference spheroid and parameters (semi-major axis/flattening). Custom datums can be saved for future use.
    • Reference Spheroid: The Earth's spheroid is a mathematical surface approximating the geoid. Selection of appropriate spheroid parameters depends on regional characteristics. Common spheroids in China include: Krasovsky 1940 (semi-major axis 6,378,245.0m, flattening 1/298.3) and International 1975 (semi-major axis 6,378,140m, flattening 1/298.257).
      • Predefined Reference Spheroid: Click the drop-down button to select a predefined spheroid type.
      • Custom Reference Spheroid: Enter a new name to create a custom spheroid, enabling modification of semi-major axis and flattening values.
    • EPSG Code: Existing spheroids, projected coordinate systems, and their combinations correspond to unique ID codes in the EPSG dataset. These EPSG Codes represent specific spheroids, units, geographic coordinate systems, or projected coordinate systems, with IDs varying by coordinate system configuration.
    • Prime Meridian: Defines the origin of longitude values. Most coordinate systems use Greenwich (0° longitude) as the prime meridian. Click the drop-down button to select a predefined prime meridian type.
  3. After configuring these parameters, the new geographic coordinate system will be created.

Related Topics

Projection Settings

Create a New Projected Coordinate System

Create Coordinate System by EPSG Encoding

Set Planar Coordinate System

Set Projected Coordinate System

Set Geographic Coordinate System