Unlike magnetic north, which is indicated by a compass, true north is the direction that points directly towards the geographic North Pole . It is defined as a line from any point on the earth’s surface to the north pole. All lines of longitude run towards true north where they eventually intersect at the north pole. In modern engineering surveys, true north is often used as the datum to determine the bearing. Therefore, people have used many different methods to find "north", such as astronomical north search, geomagnetic north search, inertial north search, and electromagnetic north search.
History
In 1852, the French scientist Foucault J proposed the idea of using a gyroscope to find the north. Limited by the technical conditions at that time, he used the method of pulling the rope by humans to drive the gyro rotation, which could not meet the requirements of north search in terms of rotation and stability accuracy. Although the experiment was ultimately unsuccessful, it opened a new chapter in human inertial north search.
In 1908, Germany's Anschutz H and Schuler finally developed the world's first practical gyrocompass. This is the first time in human history that mechanical principles have been successfully applied to achieve north search..
The invention of the gyrocompass is of great significance. It not only meets the needs of ship navigation at that time, but also promotes the development of gyroscope theory. In addition, it was in the process of improving the gyrocompass that Schuler clarified the principle by taking the vertical line indicator system as an example, which laid a theoretical foundation for the development of inertial navigation platform later. After World War II, gyro theodolite and strapdown gyro north finder came into being one after another under the demand of mine engineering and low-cost north finding.
Technology
The north seeker measures the Earth's rotation angular velocity through a high-precision dual-axis dynamically tuned gyro, and determines the true north direction value of the attached carrier autonomously. The north seeker cannot move in the process of power-on north search， because the gyro rotates at a high speed. Its north-finding process requires no external reference. Besides the high latitude limit, the north-finding measurement is not affected by weather, day and night time, geomagnetic field and site visibility conditions. Gyro north seeker is a precision inertial measurement instrument, which is usually used to provide bearing reference for mobile weapon systems such as artillery, surface-to-surface missile and ground radar. In FOG-based north finding applications, most of the methods adopted are that FOG rotates at a fixed Angle and calculates the Angle relative to the north direction by determining the offset. FOG drift must be eliminated for accurate north-pointing.
As we all know, there is an important characteristic of gyroscopes is that they have fixed axis, which means that the direction of the main axis of the gyroscope in the inertial space stays the same. However, the Earth rotates around its axis, not inertial space. Therefore, when we observe the main axis of the gyroscope on the surface of the Earth, we will find that its pointing in space changes, which is the apparent motion of the gyroscope. And the secret of the gyroscope to find north comes from it.
When the gyroscope is in apparent motion, the trajectory of the endpoint of its rotor axis is a circle. If a "hem moment" is applied to the gyroscope, the trajectory will become an ellipse. And the larger the hem property, the flatter the ellipse and the shorter the motion period. The direction of the swing center of the rotor axis of the gyroscope is the true north direction. The azimuth Angle can be determined by recording the position point of the rotor axis in the horizontal plane.
Solution
Ericco mainly provides different kinds of FOG north seekers and MEMS north seekers to find true north. Our FOG north seekers have high performance, high precision and strong stability. And our MEMS north seekers are economical, efficient and small in size.Ericco not only provides standard north-seeking products but also provides various north-seeking solutions according to the customers’ special requirements. If you want to know more about the north seeker, please feel free to contact us: https://www.ericcointernational.com/
More Technical Questions
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6.The Structure of FOG North Finder
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