Sentence:  There he 'd <WSD>take</WSD> a compass heading , figure his air speed , and deduce that in a certain number of minutes he 'd be over the broad meadows of the Merrimack Valley where it would be safe to let down through the overcast and see the ground before it hit him . 
Meaning of the word marked with <WSD> tags:  ascertain or determine by measuring, computing or take a reading from a dial