degree per hour
Angular speedexact by definition
The degree per hour is π/648000 rad/s, about 4.848 × 10⁻⁶ rad/s. It is the standard unit of gyroscope bias: a navigation-grade gyro drifts under 0.01 °/h, a tactical-grade one 1 to 10 °/h, and a consumer MEMS gyro hundreds.
Watch out: Bias is only one error term. Angle random walk, quoted in degrees per square root of hour, and bias instability are separate specifications, and a gyro compared on drift alone is being compared on a third of its behaviour.
| 1 °/h | 0.0000048481368 rad/s |
The scale is set by the Earth itself, which rotates at 15.041 °/h. A gyro good enough to sense that rate can find true north without any external reference, which is what gyrocompassing is, and it is why 15 °/h is the natural dividing line between grades of instrument.