a gyro always points to a certain direction, but how is it made to point only towards north?
http://en.wikipedia.org/wiki/Gyrocompass
Note in paricular this third paragraph under "Operation":
"Another, more practical, method is to use weights to force the axis of the compass to remain horizontal with respect to the Earth's surface, but otherwise allow it to rotate freely within that plane. In this case, gravity will apply a torque forcing the compass's axis toward true north. Because the weights will confine the compass's axis to be horizontal with respect to the Earth's surface, the axis can never align with the Earth's axis (except on the Equator) and must realign itself as the Earth rotates. But with respect to the Earth's surface, the compass will appear to be stationary and pointing along the Earth's surface toward the true North Pole."
A gyro, or gyroscope, is a device that maintains a constant orientation in space. It is often used in navigation systems to determine direction. While a gyro can't inherently point only towards north, it can be combined with other components to achieve this.
To make a gyro point only towards north, it can be integrated into an inertial navigation system (INS) or a compass system. Here's how it works:
1. Inertial Navigation System (INS):
- An INS consists of a gyro and an accelerometer.
- The gyro measures the angular velocity (rate of rotation) of the system by detecting changes in rotational movement.
- The accelerometer measures linear acceleration by sensing changes in motion.
- By combining the data from both sensors, the INS can calculate the position, velocity, and orientation of the system.
- To make the gyro point towards north, the system needs an initial reference point, which could be determined by aligning the system with a known direction (north) when it is powered on.
- As the system moves, the gyro tracks any changes in its orientation and continuously adjusts to maintain the initial reference point towards north.
2. Compass System:
- A compass system relies on a combination of a gyro and a magnetometer.
- The gyro senses changes and maintains the orientation, while the magnetometer measures the Earth's magnetic field to establish the direction of magnetic north.
- By integrating the data from both sensors, the compass system keeps the gyro aligned with the magnetic north and compensates for any drift or errors in the gyro.
- The gyro continuously adjusts to align itself with the magnetic north, allowing it to always point towards that direction.
In summary, a gyro is not designed to point exclusively towards north by itself. It must be integrated into a navigation system, such as an INS or a compass system, to determine its orientation relative to the Earth's magnetic field or through other reference points.