camera_tests.py

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# This file is part of obs_base.
#
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# (https://www.lsst.org).
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import abc
import collections
import math

import lsst.geom
from lsst.afw.cameraGeom import FOCAL_PLANE, FIELD_ANGLE

__all__ = ["CameraTests"]


class CameraTests(metaclass=abc.ABCMeta):
    """
    Tests that the butler returns a useable Camera.

    In the subclasses's setUp():
        * Call setUp_camera() to fill in required parameters.
    """

    def setUp_camera(self,
                     camera_name=None,
                     n_detectors=None,
                     first_detector_name=None,
                     plate_scale=None,
                     ):
        """
        Set up the necessary variables for camera tests.

        Parameters
        ----------

         camera_name : `str`
             name of this camera
         n_detectors : `int`
            number of detectors in this camera
         first_detector_name : `str`
            name of the first detector in this camera
        plate_scale : `lsst.geom.Angle`
            plate scale at center of focal plane, as angle-on-sky/mm
        """
        fields = ['camera_name',
                  'n_detectors',
                  'first_detector_name',
                  'plate_scale',
                  ]
        CameraData = collections.namedtuple("CameraData", fields)
        self.camera_data = CameraData(camera_name=camera_name,
                                      n_detectors=n_detectors,
                                      first_detector_name=first_detector_name,
                                      plate_scale=plate_scale,
                                      )

    def test_iterable(self):
        """Simplest camera test: can we get a Camera instance, and does iterating return Detectors?"""
        camera = self.butler.get('camera', immediate=True)
        self.assertIsInstance(camera, lsst.afw.cameraGeom.Camera)
        for detector in camera:
            msg = "Failed for detector={}".format(detector)
            self.assertIsInstance(detector, lsst.afw.cameraGeom.Detector, msg=msg)

    def test_camera_butler(self):
        """Check that the butler returns the right type of camera."""
        camera = self.butler.get('camera', immediate=True)
        self.assertEqual(camera.getName(), self.camera_data.camera_name)
        self.assertEqual(len(camera), self.camera_data.n_detectors)
        self.assertEqual(next(iter(camera)).getName(), self.camera_data.first_detector_name)

    def test_plate_scale(self):
        """Check the plate scale at center of focal plane

        Check plate_scale using the FOCAL_PLANE to FIELD_ANGLE transform
        from the camera.
        """
        plate_scale = self.camera_data.plate_scale
        self.assertIsNotNone(plate_scale)
        camera = self.butler.get('camera', immediate=True)
        focalPlaneToFieldAngle = camera.getTransformMap().getTransform(FOCAL_PLANE, FIELD_ANGLE)
        focalPlaneRadiusMm = 0.001  # an offset small enough to be in the linear regime
        for offsetAngleRad in (0.0, 0.65, 1.3):  # direction of offset; a few arbitrary angles
            cosAng = math.cos(offsetAngleRad)
            sinAng = math.sin(offsetAngleRad)
            fieldAngleRadians = focalPlaneToFieldAngle.applyForward(
                lsst.geom.Point2D(cosAng * focalPlaneRadiusMm, sinAng * focalPlaneRadiusMm))
            fieldAngleRadius = math.hypot(*fieldAngleRadians) * lsst.geom.radians
            measuredScale1 = fieldAngleRadius / focalPlaneRadiusMm
            self.assertAnglesAlmostEqual(measuredScale1, plate_scale)

            focalPlanePos = focalPlaneToFieldAngle.applyInverse(
                lsst.geom.Point2D(fieldAngleRadius.asRadians() * cosAng,
                                  fieldAngleRadius.asRadians() * sinAng))
            focalPlaneRadiusMm2 = math.hypot(*focalPlanePos)
            measureScale2 = fieldAngleRadius / focalPlaneRadiusMm2
            self.assertAnglesAlmostEqual(measureScale2, plate_scale)