How much data does iphone maps (Tomtom) use?

I have no Wi-Fi. I use maps to find locations for my job. It seems as though as little as I use it, not even using it as I'm driving, my data use spikes and I'm charged extra each month. I have even just used it to take screen shots of important turns, etc., and still used lots of data. Why? Is there a way to do this by using less data, please?

It uses a lot. Data is data.

If you use maps as part of your job, why aren't you using a mobile GPS unit? Once you have the unit, there's no cost to use it.

  • Old GPS or iPhone maps or google maps app? I'm going to drive from IL down to SC and I don't trust my old garmin nuvï 255 nor iphone maps lol:-) GPS update is $50 which I'm not going to spend. So has anyone used iphone maps or google maps app on long distance trips? Or I just better use old gps?
  • IPhone: Google maps or default apple maps? I personally like the default maps, at least the OS 7 version. (like everyone else who had a brain, I hated the OS 6 version) Which one do you guys like more? Which is more popular now?
  • If I keep my data on but also use Wi-Fi will it use my data? I just got an iPhone from us cellular. I use Wi-Fi to save data, but I can't receive group messages if my data isn't on. If I keep my data on all the time, but use Wi-Fi, will it use my data? And if I keep both on will it use my Wi-Fi instead of data?
  • How to get directions on Apple maps when I don't have data? Today I was walking to some place and I checked directions before leaving home using my Wi-Fi. When I was on the sidewalk I looked at my phone and it was giving me live directions and it knew exactly where I was and how many metres till I will need to turn. I don't even have data on my iPhone so how was it giving me directions? Did I get charged? I'm in Ontario and I'm with chatr mobile. I have an iPhone 5.