指 zhǐ is pronounced jer in the third tone because zh sounds like the letter j.
指 means to point or to direct.
南 nάn means south and is pronounced in the second tone.
针 zhēn means needle and is pronounced in the first tone.
means south-pointing-needle or compass. In Chinese maps, South is at the top of the page and North is at the bottom. The needle points south in Chinese compasses, not north.