English word phototachymeter comes from English tachymeter, English photo- (Light, electromagnetic radiation. Photography.)

Detailed word origin of phototachymeter

Dictionary entry	Language	Definition
tachymeter	English (eng)	A speed indicator; a tachometer.. A surveying instrument for quickly finding distances.
photo-	English (eng)	Light, electromagnetic radiation. Photography.
phototachymeter	English (eng)	An electrooptical instrument for measuring distances.

Words with the same origin as phototachymeter