MathTransform created using Proj.createFromUserInput with inline pipeline does not work (example included)

[eLvErDe]

Hello,

I'm trying to use your module because I need to apply custom transformation pipeline. However, it does not work.
I made a very simple example showing the issue, with incorrect values being returned while command line cct example works.

import java.util.Arrays;
import java.util.stream.Collectors;

import org.opengis.referencing.operation.MathTransform;
import org.opengis.referencing.operation.TransformException;
import org.opengis.util.FactoryException;
import org.osgeo.proj.Proj;

public class DebugProjJni {

	/**
	 * Working command line example <a href="https://proj-tmp.readthedocs.io/en/docs/operations/conversions/push.html#examples">here</a>
	 * 
	 * @throws TransformException
	 */
	public static void main(String[] args) throws FactoryException, TransformException {

		String pipeline = "+proj=pipeline +step +proj=push +v_3 +step +proj=cart +ellps=GRS80 +step +proj=helmert +x=3000 +y=1000 +z=2000 +step +proj=cart +ellps=GRS80 +inv +step +proj=pop +v_3";
		MathTransform transform = (MathTransform) Proj.createFromUserInput(pipeline);

		double[] input = { 12, 56, 12.3, 2020 };
		double[] output = new double[input.length];

		transform.transform(input, 0, output, 0, 1);

		System.out.println(String.format("Source: %s, Target: %s",
				Arrays.stream(input).mapToObj(String::valueOf).collect(Collectors.joining(" ")),
				Arrays.stream(output).mapToObj(String::valueOf).collect(Collectors.joining(" "))));

		// Result is: Source: 12.0 56.0 12.3 2020.0, Target: 1.5671188250836727E-4 0.0 0.0 0.0
		// Should be: 12.0056753463 55.9866540552 12.3000 2000.0000
	}

}

Either I'm a complete idiot or there is something here that does not work as expected.
For the record getSourceDimensions() and getTargetDimensions() both return 0 and I think it might be related...

Best regards, Adam.

[desruisseaux]

The module needs a non-zero number of dimensions. The value of zero is probably because the result of Proj.createFromUserInput(pipeline) is not associated to source and target CRS. We need to check how to modify the getDimension(int) method for getting the correct number of dimensions from that result.

[eLvErDe]

So, you confirm it is indeed a bug ?

[desruisseaux]

Rather a request of enhancement. That method is for creating CRS, coordinate system, datum, etc., which are objects defined by the ISO 19111 international standard. Pipelines are PROJ-specific. It is reasonable to want to construct them, but it may need to be handled as a special case (need investigation before to confirm).

[eLvErDe]

Okay.

Thing is, Java GIS ecosystem seems pretty awful to me and I found no way to use a custom 3D projection pipeline (not working in GeoTools, PROJ4J, Apache SIS) but this is working perfectly fine in Python or with libproj cli tools.

That's why I wanted to switch PROJ-JNI.

I ended up writing a wrapper around cct command line tool, probably a nightmare from a performance perspective but that's all I get !

[desruisseaux]

3D projection should work. They can be described in standard ISO 19162 Well Known Text (WKT), and at least PROJ and Apache SIS should be able to parse those WKT. Have you tried to describe your CRS using such WKT?