While you could zoom in and out in Apple Maps before using finger gestures, iOS 11 just made it easier to do so using only one hand. It may not be the biggest feature in the world, but sometimes it's the littlest of things that can really make the iPhone experience better.
Before we get into the new zooming trick in iOS 11, let's talk about the gestures that worked before — and still do (and probably forever will).
First up, pinch-to-zoom. This is what everyone is used to by now. Just use two fingers to pinch and zoom out of the map, or spread two fingers apart to zoom in. It's that simple. Next, there's the double-tap with one finger, which zooms in each time you perform the gesture. And lastly, there's tap with two fingers, which will zoom out. What's odd about this last one is that it zooms out more than you zoomed in with the double-tap gesture.
To use Maps one-handed on your iPhone in iOS 11, you would still use the same double-tap with one finger to zoom in on the map. That hasn't changed since it's easy to perform with a thumb while you're holding your iPhone toward you. But there's now another way, plus a way to zoom out with your thumb only.
Just double-tap and hold. Yep, it's very similar to the double-tap to zoom method, only instead of releasing after the second tap, you're going to hold your thumb (or whatever finger) on the screen. Then just move your finger northward to zoom in and southward to zoom out.
You can't move perfectly side to side at 180 degrees, but anything other than that will make the map zoom in the appropriate manner, and give you more granular control at how fast or slow you're zooming in or out.
So now when you're walking about looking at a Map in one hand on your iPhone and holding a coffee in the other, you can actually zoom in and out on the screen without thinking twice. It's a nice little touch to the Maps app in iOS 11.