One of several new features in iOS 12.2 is the addition of the Air Quality Index to the Maps app. The AQI is a measurement of air quality that takes into account ground level ozone, particulates (which includes things like ash and pollen), carbon monoxide, sulfur dioxide and nitrogen dioxide.
Punching in your home address (or work or any common destination) in your favorite navigation app grows tiresome after a while, even if it is already there in your recent places. Thankfully both Waze and Google Maps offer shortcuts to directions to your favorite places through a simple 3D Touch and a tap. All you have to do is assign your home, work, etc. locations, then they will be available for quick navigation. Apple Maps, as you would expect, is supposed to have this functionality as well, but as of this writing it is not working properly in iOS 11.3
iOS 8 introduced 3D Flyover tours of various cities around the world, but they were guided in a sense - they flew you around the city as you sat back and watched. In iOS 11 you can control your flyover (though the guided flyovers are still available). To do so, search for a city, then tap the Flyover button. You can start the guided flyover with the "Start City Tour" button or control your own motion simply by tapping elsewhere on the screen.
One-handed zoom can be useful in plenty of situations. To use it, simply double tap the screen but keep your thumb on the screen after the second tap (so double tap and hold), then slide your thumb up to zoom in or down to zoom out. Once you release you will have to double tap again to use the feature again.
With every new iOS release come several new features that Apple enthusiastically introduces during its annual WWDC event, while a plethora of smaller features go unmentioned. The introduction of iOS 11 followed suit, spotlighting major changes to Control Center and screen shots, new AirPod controls and Screen Recording.