How did they manage to land exactly in the same spot in every planet?!

I dunno if this has been asked elsewhere.Given the size of all the three planets ..millers, Edmunds and Mann how did the ranger exactly land close to the location where dr Miller, Mann and Edmund had previously landed?! May be the signalling beacon on mann's and Miller's planet was used as a guide but with no any form of signal from Edmunds planet how did Brand land exactly where Dr Edmund had landed first?