I just downloaded the Navionics app for Android. It was $10. Some (Minnesota) lakes are more accurate than others, but the app will get me close enough to be well worth the $10. I'll just mark the map on my phone with the depth that I read when I drill, so I'll know the next time. Also, you can mark your hot spots and no one else can see them, unless you upload them somehow.
If I head to a new lake, I'll go to the DNR Lake Maps website and double-check the depths and contours. There is a lake out by me, Little Long Lake, that had HUGE discrepancies between the Navionics app and the DNR lake map. The two were literally off by 20ft. Well, the DNR map was correct, but I didn't know that until I started drilling. No big deal. I just marked those depths on my app. Another lake about the same size, just down the road, was pretty darn accurate on the Navionics app and was similar on the DNR map.
All-in-all, it's worth the $10. Don't expect it to be perfect, but once you get used to it, I think you'll find it super useful.
