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title: Add vertical and temporal axes to an horizontal CRS

This example creates a 4-dimensional Coordinate Reference System (CRS) with an horizontal, a vertical and a temporal component. While it is possible to create a CompoundCRS programmatically, it is much easier to do that from authority codes when those codes exist. There is two syntaxes standardized by the Open Geospatial Consortium (OGC): One syntax using an identifier starting with http://www.opengis.net/def/crs-compound followed by the components in the query part of the URL, and a shorter but less common syntax starting with urn:ogc:def:crs. Apache SIS accepts both, illustrated below.

Direct dependencies

Maven coordinates	Module info
org.apache.sis.storage:sis-referencing	org.apache.sis.referencing

Code example

import org.apache.sis.referencing.CRS;

public class Compound {
    /**
     * Demo entry point.
     *
     * @param  args  ignored.
     * @throws FactoryException if an error occurred while creating the CRS
     *         or searching for a coordinate operation.
     */
    public static void main(String[] args) throws FactoryException {
        var crs = CRS.forCode(
                "http://www.opengis.net/def/crs-compound?"+
                "1=http://www.opengis.net/def/crs/epsg/0/4326&"+
                "2=http://www.opengis.net/def/crs/epsg/0/5714&" +
                "3=http://www.opengis.net/def/crs/OGC/0/JulianDate");
        /*
         * The following is a more compact way to request the same CRS.
         * If (longitude, latitude) axis order is desired, just replace
         * "EPSG::4326" by "OGC::84".
         */
        var alternative = CRS.forCode("urn:ogc:def:crs,crs:EPSG::4326,crs:EPSG::5714,crs:OGC::JulianDate");

        System.out.println(crs);
        System.out.println();
        System.out.println("Compact alternative is equal: " + crs.equals(alternative));
    }
}

Alternatively, if the components are already available as CoordinateReferenceSystem object, the compound method can be invoked instead.

Output

CompoundCRS["WGS 84 + MSL height + Julian",
  GeodeticCRS["WGS 84",
    Datum["World Geodetic System 1984",
      Ellipsoid["WGS 84", 6378137.0, 298.257223563]],
    CS[ellipsoidal, 2],
      Axis["Geodetic latitude (Lat)", north],
      Axis["Geodetic longitude (Lon)", east],
      Unit["degree", 0.017453292519943295],
    Id["EPSG", 4326, "9.9.1"]],
  VerticalCRS["MSL height",
    VerticalDatum["Mean Sea Level"],
    CS[vertical, 1],
      Axis["Gravity-related height (H)", up],
      Unit["metre", 1],
    Id["EPSG", 5714, "9.9.1"]],
  TimeCRS["Julian",
    TimeDatum["Julian", TimeOrigin[-4713-11-24T12:00:00.000]],
    CS[temporal, 1],
      Axis["Time (t)", future],
      TimeUnit["day", 86400],
    Id["OGC", "JulianDate"]],
  Area["World."],
  BBox[-90.00, -180.00, 90.00, 180.00]]

Compact alternative is equal: true