If you, like me, play Ingress, and your current version is 1.18.1, you may have noticed that sometimes when the Ingress app goes to background and it's later called back to the screen, the GPS is off and it won't get a location fix to save your life!
So, the hard way to "fix" this--use a task-killer and end Ingress, then restart it.
However, there *is* a handy work-around:
Fire up Google Maps (before starting Ingress), and set it to give you turn-by-turn navigation directions to somewhere (anywhere, as long as you're not actually going there). Then, mute the voice.
Et viola! You can switch to and from Ingress at-will and it'll have perfect GPS locationality (is that a word?) the whole time.