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Coordinates (~ctapipe.coordinates)

ctapipe.coordinates

Introduction

ctapipe.coordinates contains coordinate frame definitions and coordinate transformation routines that are associated with the reconstruction of Cherenkov telescope events. It is built on astropy.coordinates, which internally use the ERFA coordinate transformation library, the open-source-licensed fork of the IAU SOFA system.

Getting Started

The coordinate library defines a set of frames, which represent different coordinate reprentations. Coordinates should be described using an astropy.coordinates.SkyCoord in the appropriate frame.

The following special frames are defined for CTA:

  • CameraFrame
  • EngineeringCameraFrame
  • TelescopeFrame
  • NominalFrame
  • GroundFrame
  • TiltedGroundFrame

they can be transformed to and from any other astropy.coordinates frame, like astropy.coordinates.AltAz or astropy.coordinates.ICRS (RA/Dec)

The two different coordinate frames are shown here:

../examples/plot_camera_frames.py

The CameraFrame is used internally in ctapipe and comes from sim_telarray. It abstracts the transformation differences between 1 and 2 mirror telescopes away. The EngineeringCameraFrame is used by MAGIC, FACT and the H.E.S.S. analysis software.

Reference/API

ctapipe.coordinates

ctapipe.coordinates.camera_frame

ctapipe.coordinates.telescope_frame

ctapipe.coordinates.nominal_frame

ctapipe.coordinates.ground_frames