Determining how far an object is from you often requires comparison against a second object of known distance.

Cones cannot detect color by themselves; rather, color vision requires comparison of the signal across different cone types.

Distinguishing between P. axanthus and P. striatus is more difficult, requiring comparison of patterns with a field guide, known distribution, or a karyotype test.

True critical learning requires cross-cultural comparison; non-cross-cultural learning aided by a skilled teacher is not true critical learning.

This requires timely locating and comparison of captured data with planning.

Full identification requires comparison of the specimen with some authoritative source, such as a full and accurate description of the species, preferably in a monograph.

To compare "full-spectrum" sources requires direct comparison of spectral distributions.

Understanding the economy requires comparison not only with the last year but also with the last generation.

Interpreting results requires some experience, or comparison with a good capacitor, and depends upon the particular meter and range used.

Neither law explicitly requires comparison to suburban communities nor restricts comparison to other city employees.