Considering GPS was originally created for military purposes, I find it fascinating that the largest holes are over the north and south poles. The northern polar region is where the US-launched missiles and bombers would travel. Does the lesser orbital coverage in that area not negatively affect GPS precision?
Bombers use a similar inertial guidance system, but with updates from GPS and star trackers as applicable. The reduced precision from GPS doesn't matter too much, as the inertial guidance systems are pretty good now.
A surprising number of ICBMs have used star trackers as well! It's somewhat surprising that ICBMs used star trackers before inertial guidance was sufficiently precise. The idea of an automated, high-precision star tracker is not so surprising today but back in the '60s it was quite an achievement.
I don't believe ICBM's are using GPS. They're programmed like they always have been and follow a very predictable path and don't change course (unlike hypersonic missiles). It's the "smart weapons" that are usually plane/ship dropped/launched that are gps guided as they are smaller munitions that have a much smaller blast radius and need to be more precise to be effective (as opposed to just carpet bombing the whole area). Those are "close" range weapons. You don't need to be very precise with an ICBM to obliterate the target, as it's usually city-sized. A mile off here or there will still destroy the target. Planes can and do still fly without GPS. There also haven't been too many wars involving the poles as basically no one lives there except science teams and no one wants the "land" as you can't do anything economically practical with it. Most of our ICBM's are still ancient Minuteman III's which were manufactured in the 1960's (my dad launched one in 68 out of Minot AFB, ND) and recently updated in 2015 to extend their useful life.
