What does this number measure?
Size calculated from the mean radius published by NASA/JPL: the diameter of a sphere with equivalent volume. The actual shape of small moons can be highly irregular.
Compare the stated dimensions
The comparison uses the number in each fact sheet: altitude, height, diameter, length or distance, depending on the reference. Two values in metres do not necessarily describe the same property.
Source and limitations
Catalogue value: a source is provided, but the measurement has not been individually audited in this project.
Uncertainty stated in the catalogue: about 480 m.
Irregular shape and dusty surface inspired by observations of Deimos; fine details are interpreted. Volume-equivalent diameter, not the silhouette's length.