Texting and driving is a pretty heinous crime. Bad enough that it's spawned entire ad campaigns devoted to educating the public on the dangers of such acts. Of this, you are no doubt aware. What you may be less aware of is the fact that figuring out where you're going is exactly as dangerous as sending someone a message that says "Doesn't the Peachoid look like a giant..."
California, despite having no known Peachoids, knows this very well and a court has ruled that using a mapping application is just as bad (and illegal) as texting behind the wheel. This isn't the first time California has come down hard against GPS in cars. For a while, it was illegal to mount a navigation unit anywhere on your windshield, though starting January 1, 2009, a new law allowed them to be displayed in the lower left or right corners of your field of view, which some motorists found to be unsatisfactory.
The court did recognize that there was room to argue that the law banning any hands-on use of electronic devices was a bit arbitrary, but unfortunately, that's not for the courts to decide. As the law is written in California, you simply cannot use your maps app while driving.
Or at least, you can't touch it. As long as you set up your navigation route before you leave, place your phone in a dashboard mount that fits in a 5"x5" area in the lower-left corner or 7"x7" area in the lower-right hand corner of your windshield such that it doesn't impair your field of vision, and do not interact with it unless in a hands-free manner...everything should be fine.