tachymeter vs tacheometer

tachymeter and tacheometer both are nouns.

Word	Noun	Adjective	Verb	Adverb
tachymeter	Yes	No	No	No
tacheometer	Yes	No	No	No

As nouns, tachymeter and tacheometer are synonyms defined as:

tachymeter and tacheometer: a theodolite designed for rapid measurements

tachymeter (noun)	tacheometer (noun)
a theodolite designed for rapid measurements	a theodolite designed for rapid measurements