He closed the manual. For the first time in forty years at sea, Haruki Saito turned off the gyrocompass and steered by the stars. The Mirai Maru continued through the trench. And somewhere below, the Earth turned in a way that Yokogawa had not anticipated.
"This instrument is designed to find north. It is not designed to understand why north moves." yokogawa gyro compass cmz 700 user manual
Saito looked at the chart. The Mirai Maru was crossing the Kuril Trench, where the Pacific Plate grinds beneath the Okhotsk Plate. The seabed was a graveyard of basalt and serpentinite—dense, magnetic, heavy. The manual did not have a page for "subduction zone metaphysics." But it had an appendix: He closed the manual
"Local variations in gravitational gradient exceeding 0.0003 m/s² may induce a precession torque on the gyroscopic element. The CMZ 700 will reject up to 0.0005. Beyond that, output is undefined." And somewhere below, the Earth turned in a
Page 1-2: "The CMZ 700 utilizes a dynamically tuned ring laser gyro. No moving parts. Settling time: 3 hours." No moving parts. That felt wrong to Saito. A ship without a spinning wheel of bronze and copper was like a heart without a beat. But the numbers were seductive. Accuracy: 0.01 degrees secant latitude. Mean time between failure: 50,000 hours.