hydrography vs oceanology

hydrography and oceanology both are nouns.

Word	Noun	Adjective	Verb	Adverb
hydrography	Yes	No	No	No
oceanology	Yes	No	No	No

As nouns, oceanology is a hypernym of hydrography; that is, oceanology is a word with a broader meaning than hydrography:

hydrography: the science of the measurement and description and mapping of the surface waters of the earth with special reference to navigation
oceanology: the branch of science dealing with physical and biological aspects of the oceans

Other hypernyms of hydrography include oceanography.

hydrography (noun)	oceanology (noun)
the science of the measurement and description and mapping of the surface waters of the earth with special reference to navigation	the branch of science dealing with physical and biological aspects of the oceans