When your target objects are sufficiently ellipse-like, you can use the measurements below to quantify the various parameters of the ellipse.
For details of how the elliptical parameters are measured, see Measuring elliptical parameters.
For non-parametric morphological measurements, see Morphology measurements (non-parametric).
The measures that start with `--geo-*` ignore the pixel values and just do the measurements on the label’s “geometric” shape.

`--semi-major`The pixel-value weighted root mean square (RMS) along the semi-major axis of the profile (assuming it is an ellipse) in units of pixels.

`--semi-minor`The pixel-value weighted root mean square (RMS) along the semi-minor axis of the profile (assuming it is an ellipse) in units of pixels.

`--axis-ratio`The pixel-value weighted axis ratio (semi-minor/semi-major) of the object or clump.

`--position-angle`The pixel-value weighted angle of the semi-major axis with the first FITS axis in degrees.

`--geo-semi-major`The geometric (ignoring pixel values) root mean square (RMS) along the semi-major axis of the profile, assuming it is an ellipse, in units of pixels.

`--geo-semi-minor`The geometric (ignoring pixel values) root mean square (RMS) along the semi-minor axis of the profile, assuming it is an ellipse, in units of pixels.

`--geo-axis-ratio`The geometric (ignoring pixel values) axis ratio of the profile, assuming it is an ellipse.

`--geo-position-angle`The geometric (ignoring pixel values) angle of the semi-major axis with the first FITS axis in degrees.

GNU Astronomy Utilities 0.22 manual, February 2024.