The turn-by-turn navigation features of modern smart phones are so good they've almost entirely replaced standalone GPS units. But in actual use, many drivers take their eyes off the road to check the map, which can be extremely unsafe. Even if you have a car mount to keep your phone in your field of vision, using it for navigation can still result in diverting your attention from the road, however briefly. The built-in navigation systems in many cars have the same problem.
Head up displays (HUDs) were developed for military applications to allow pilots to see important data while (literally) keeping their heads up and eyes forward, rather than looking down at instruments. HUDs are starting to appear as options in new cars in the form of displays embedded in the car's dash that reflect onto the windshield. Garmin offers a version of this feature with its Garmin HUD, a display accessory that can be placed on the dashboard to reflect navigation data from company's apps.
Simple projection, a complex app, and a heavy battery burden
Another navigation app, Sygic GPS Navigation for Android and iOS, was recently updated with its own HUD feature ($5 in-app purchase). It works similarly to Garmin's HUD, but without requiring extra hardware.
Tapping the HUD button on the app's navigation screen enables a simplified, high-contrast navigation display. Simply place your phone on your car's dashboard, and the reversed display reflects on your car's windshield, showing the distance and direction of the next turn, your current speed and the road's speed limit (which I found particularly handy). It also shows whether you're near any of the speed cameras in the company's database and your estimated time of arrival.
I'll admit, the feature initially struck me as gimmicky (though clever), but after using it, I'm impressed. Despite the iPhone's relatively small screen, the display was easy to read when reflected on the windshield (at least at night), especially if I upped the brightness on my device. I do recommend using an external power source, as the app can drain your battery quickly (albeit it about as quickly as other navigation apps I've used). A more significant drawback is that the HUD feature really only works at night — in my testing, the display wasn't bright enough to overcome ambient sunlight. Sygic is up-front about this limitation.
Another consideration is that the feature is only as useful as the underlying Sygic app. In my testing, I found the app powerful, but frequently frustrating. The user interface is often confusing, the search feature finicky, and while the app is highly configurable and offers features not found in map apps from Apple and Google, these choices can be overwhelming. The app also behaves strangely sometimes — good luck navigating to a faraway location if you're missing maps for intervening regions or your destination, for example.
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