Why don't you have a GPS handheld with gyro? MONEY.
I remember when FEDEX wanted to get the COMPASS on the MEL list...yes, you could dispatch without a compass. The FAA actually said no on that one.
Kudos to the crew and too damn bad a huge plane with such redundency up the wazoo can be almost be brought down by overflowing water.
cheap...its all money boys and girls!