Wrong Camera Coordinate Frame in LST Camera defintion

[maxnoe]

As discussed with @FrancaCassol and @rlopezcoto in Lugano,
the file LSTCam-002.camgeom.fits.gz in ctapipe-extra
has the pixel coordinates in the wrong cordinate frame.
The coordinates are in MAGIC/FACT/EngineeringFrame not in the
HESS/sim_telarray/ctapipe frame.

ctapipe at the moment requires that the pixel coordinates are given in the sim_telarray frame, otherwise coordinate transformations will not work.

from ctapipe.instrument import CameraGeometry
from ctapipe.visualization import CameraDisplay
import matplotlib.pyplot as plt
import numpy as np

fig, axs = plt.subplots(1, 2, constrained_layout=True, figsize=(6, 3))

d1 = CameraDisplay(CameraGeometry.from_name('LSTCam', version=2), ax=axs[0])
d2 = CameraDisplay(CameraGeometry.from_name('LSTCam'), ax=axs[1])
d1.image = np.arange(1855)
d2.image = np.arange(1855)


fig.savefig('lstcams.png', dpi=300)

[maxnoe]

See the documentation of CameraFrame:
https://cta-observatory.github.io/ctapipe/api/ctapipe.coordinates.CameraFrame.html#ctapipe.coordinates.CameraFrame

Discussion here cta-observatory/ctapipe#255

[maxnoe]

I opened a PR here: cta-observatory/ctapipe#1085

If that is merged, you could do:

cam = CameraGeometry.from_name('LSTCam', version=2)
cam.frame = EngineeringCameraFrame()
cam = cam.transform_to(CameraFrame())

To get the camera geometry in the correct coordinate system.

[rlopezcoto]

Great @maxnoe, thanks!
Since we are not in a very big hurry because we are still not taking data in which we use the pointing information, I think by now we will wait to see if the PR gets merged, otherwise we can consider other actions

[maxnoe]

I would suggest to fix the file as well. So x → -y, y → -x, and cam and pix rotation → 90° - rotation

[maxnoe]

cta-observatory/ctapipe#1085 is merged now, the EngineeringCameraFrame is available and can be used for plotting. However, the geometry files needs to have coordinates given in the CameraFrame, so this should be updated

[rlopezcoto]

This was solved with this ctapipe-extra PR and we later moved them to ctapipe_io_lst:
cta-observatory/ctapipe_io_lst#19
cta-observatory/ctapipe_io_lst#20
cta-observatory/ctapipe_io_lst#23