Originally Posted by
Goldenrivett
The IRS determines the direction of True North by measuring the direction of apparent wander of its “giros” in 3 directions, due to Earth’s rotation. The rate of apparent wander enables it to determine the Latitude. When we insert present position, it compares the value to its calculated Latitude, but it needs Longitude because that can’t be determined.
That makes sense! So the IRS just compares both latitudes, and if both matches, it will then take/add GPS longitude to it. That explains it, thank you!