You don't need the connectivity all the time; it is enough when calculating the initial route. After that, GPS signal is enough, and can be intermittent (in tun

You don't need the connectivity all the time; it is enough when calculating the initial route. After that, GPS signal is enough, and can be intermittent (in tunnels or deep valleys, for example). But I've seen another uses of dedicated GPS appliances: bikers. They use rugged ones, they don't break so easily as phones.