Abstract As we all know, Surrey has pioneered the use of GPS on small satellites, but how does a GPS receiver work, and how is it used in space? This talk will discuss the basics of the GPS receiver, what benefits GPS offers to a satellite, and Surrey's history of spaceborne GPS experiments. Originally Surrey purchased GPS receivers for use in space, but recently, Surrey has developed its own receiver in collaboration with ESA. Surrey's Space GPS Receiver (SGR) is now in continuous operation on UoSAT-12. The experiment has achieved a number of world firsts, and the SGR remains in many ways the most advanced GPS receiver in orbit today. This talk will outline some of the interesting and surprising research topics that GPS has opened up for Surrey, and look at plans for the future.