DistortionCorrectionSIP

class ctapointing.camera.DistortionCorrectionSIP(**kwargs: Any)

Bases: DistortionCorrection

Class implementing simple polynomial distortion correction for images

Pixel corrections are implemented according to “The SIP Convention for Representing Distortion in FITS Image Headers”

Currently, a 2nd order polynominal correction is implemented. For the transformation from ideal (intermediate) pixel coordinates to physical pixel coordinates:

\[ \begin{align}\begin{aligned}x_p = A_{10} x^1 y^0 + A_{20} x^2 y^0 + A_{11} x^1 y^1 + A_{02} x^0 y^2\\y_p = B_{10} x^1 y^0 + B_{20} x^2 y^0 + B_{11} x^1 y^1 + B_{02} x^0 y^2\end{aligned}\end{align} \]

For the inverse transformation from physical pixel coordinates to ideal (intermediate) pixel coordinates:

\[ \begin{align}\begin{aligned}x = AP_{10} x_p^1 y_p^0 + AP_{20} x_p^2 y_p^0 + AP_{11} x_p^1 y_p^1 + AP_{02} x_p^0 y_p^2\\y = BP_{10} x_p^1 y_p^0 + BP_{20} x_p^2 y_p^0 + BP_{11} x_p^1 y_p^1 + BP_{02} x_p^0 y_p^2\end{aligned}\end{align} \]

Attributes Summary

coeff	An instance of a Python dict.
coeff_inv	An instance of a Python dict.

Methods Summary

apply_correction(coords)	Apply distortion correction from ideal (intermediate) pixel coordinates (x, y) to physical pixel coordinates (xp, yp).
apply_inverse_correction(coords_p)	Apply distortion correction from physical pixel coordinates (xp, yp) to ideal (intermediate) pixel coordinates (x, y).

Attributes Documentation

coeff

An instance of a Python dict.

One or more traits can be passed to the constructor to validate the keys and/or values of the dict. If you need more detailed validation, you may use a custom validator method.

Changed in version 5.0: Added key_trait for validating dict keys.

Changed in version 5.0: Deprecated ambiguous trait, traits args in favor of value_trait, per_key_traits.

coeff_inv

An instance of a Python dict.

One or more traits can be passed to the constructor to validate the keys and/or values of the dict. If you need more detailed validation, you may use a custom validator method.

Changed in version 5.0: Added key_trait for validating dict keys.

Changed in version 5.0: Deprecated ambiguous trait, traits args in favor of value_trait, per_key_traits.

Methods Documentation

apply_correction(coords)

Apply distortion correction from ideal (intermediate) pixel coordinates (x, y) to physical pixel coordinates (xp, yp).

Parameters:

coords (np.array) – 2D array of ideal pixel positions

Returns:

coords_p – 2D array of physical pixel positions

Return type:

np.array

apply_inverse_correction(coords_p)

Apply distortion correction from physical pixel coordinates (xp, yp) to ideal (intermediate) pixel coordinates (x, y).

Parameters:

coords_p (np.array) – 2D array of physical pixel positions

Returns:

coords – 2D array of ideal pixel positions

Return type:

np.array

apply_correction(coords)

Apply distortion correction from ideal (intermediate) pixel coordinates (x, y) to physical pixel coordinates (xp, yp).

Parameters:

coords (np.array) – 2D array of ideal pixel positions

Returns:

coords_p – 2D array of physical pixel positions

Return type:

np.array

apply_inverse_correction(coords_p)

Apply distortion correction from physical pixel coordinates (xp, yp) to ideal (intermediate) pixel coordinates (x, y).

Parameters:

coords_p (np.array) – 2D array of physical pixel positions

Returns:

coords – 2D array of ideal pixel positions

Return type:

np.array