ordnance datum

14 LETTERS · STARTS WITH O

ordnance datum is a valid 14-letter word worth 19 points in Scrabble and 24 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

O1R1D2N1A1N1C3E1D2A1T1U1M3

1 + 1 + 2 + 1 + 1 + 1 + 3 + 1 + 0 + 2 + 1 + 1 + 1 + 3 =19 PTS

DOUBLE WORD → 38TRIPLE WORD → 57

MEANING

What does ordnance datum mean?