navigational instrument

NOUN
23 LETTERS · STARTS WITH N

navigational instrument is a valid 23-letter word worth 28 points in Scrabble and 37 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
N1A1V4I1G2A1T1I1O1N1A1L1I1N1S1T1R1U1M3E1N1T1
1 + 1 + 4 + 1 + 2 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 0 + 1 + 1 + 1 + 1 + 1 + 1 + 3 + 1 + 1 + 1 =28 PTS
DOUBLE WORD → 56TRIPLE WORD → 84
MEANING

What does navigational instrument mean?