pybsm.metrics.functional.giqe4

pybsm.metrics.functional.giqe4(*, rer: float, gsd: float, eho: float, ng: float, snr: float, elev_angle: float) → tuple[float, float]

General Image Quality Equation version 4 from Leachtenauer, et al.

“General Image Quality Equation: GIQE,” Applied Optics, Vol 36, No 32, 1997. The use of GIQE 4 is not endorsed but it is added to pyBSM for historical completeness.

Parameters:

  • rer – geometric mean relative edge response (unitless)

  • gsd – geometric mean ground sample distance (m) before projection into the ground plane

  • eho – geometric mean edge height overshoot (unitless)

  • ng – noises gain, i.e. increase in noise due to sharpening (unitless); if no sharpening is applied then ng = 1

  • snr – contrast signal-to-noise ratio (unitless)

  • elev_angle – sensor elevation angle as measured from the target (rad), i.e. pi/2-nadir_angle. See pybsm.geospatial.nadir_angle for more information. Note that the GIQE4 paper defines this angle differently but we stick with this version to be consistent with the GIQE 5 code. The outcome is the same either way.

Returns:

niirs :

a National Image Interpretability Rating Scale value (unitless)

Raises:
ZeroDivisionError:

error raised when snr is 0