You can get fine enough coordinates (within 0.1 NM) from the 10-9 page if there are not any discrete gate coordinates.
Today's Laser Ring Gyro IRUs are pretty accurate, even without updating. Old IRUs with mechanical gyros were much more sensitive to initial position accuracy. Also, the software that integrated them into the nav system was a key factor in how well they would take and hold an update. Still, it was possible to get good accuracy after starting from a moving aircraft carrier, as long as the IP was within 1/2 mile or so and the initial ship's velocity was accurately input...