Sometimes a terrible old movie is only watchable when you add an audio track in which it’s being brutally and relentlessly mocked: this was the MO of Mystery Science Theater 3000 and RiffTrax, the latter featuring plenty of MST3K alumni. Such is the case with this 1949 educational film, late 1949, “What Is a Map,” which takes an awfully long time to (a) well, do much of anything and (b) get to the subject of maps, so RiffTrax’s version makes it a bit easier to stomach. A bit.