A north finder is a type of compass that is used to find the true north value of a certain position. Gyro North finder, also known as gyro compass, is an inertial measurement system that uses gyro principle to determine the projection direction of the Earth’s rotation rate in the local horizontal plane (that is, true north position). Its north finding process requires no external reference. In addition to being limited by high latitude, its north finding survey is not affected by weather, day and night time, geomagnetic field and site visibility conditions.
Gyroscope north finder can be divided into the following three types:
(1).A north finder using a two-degree-of-freedom gyroscope as an Earth rotation sensor (e.g. a pendulous gyro north finder); (2).A north finder using a single-axis rate gyroscope as a sensor (e.g. strap down gyroscope north finder); (3).A north finder using a triaxial-axis dynamic gyroscope as a sensor (e.g. dynamic gyro north finder).
Platform north finding system
As a key technology of navigation system, The low-cost 3-axis FOG North finder ER-NFS-03 consists of an inertial measurement unit (IMU), a digital signal processing unit, and a mechanical component mechanism. It can provide true north azimuth for the carrier north-seeking technology is not only widely used in satellite, missile, artillery, ship inertial navigation and other fields, known as attitude measurement and national defense high-tech field, but also in geophysical exploration, coal mining, Geodetic surveying and other fields are also widely used. North finder is one of the important equipments using north-seeking technology, and it has also become a necessary measurement method.
The north finder can complete the data reception of gyroscope, accelerometer and external GPS, system error compensation calculation, navigation scheme, and send real-time navigation information such as speed, position and attitude through the monitoring port in a specified period.The high precision fiber optic gyro north finder ER-NFS-02 has the characteristics of strong stability and high reliability. At the same time, it is a dynamic working mode with high precision and high reliability. It provides information about the movement, speed and position of the vehicle. It is suitable for missile launch, weapon aiming, radar, antenna, vehicle and other dynamic initial calibration, static initial calibration, direction control and other objects.
Dynamic north finding refers to the use of the dynamic effect of the interaction between the rotation of the gyro and the rotation of the earth, such as the gyro compass and the gyro theodolite. Motion north-seeking refers to north-seeking by measuring the horizontal component of the angular velocity of the earth’s rotation through a gyroscope, and the earth rotates around the earth at a constant self-reflection angular velocity ωe. For a point on the Earth of dimension φ, the Earth’s angular velocity at that point can be decomposed into two components: the horizontal component ωe1 = ωecosφ, which points to true north along the Earth’s meridian, and the vertical component ωe2 = ωesinφ, which goes vertically upward along the Earth’s vertical line. Using inertial technology to measure the horizontal component of the angular velocity of the earth’s rotation, the north information of the measured point on the earth can be obtained. Strapdown north-seeking gyroscopes fall into this category.
The principle of ERICCO’s fiber optic north finder ER-FNS-03 is to use the strapdown compass effect to find the true north direction. The composition is composed of three-axis gyroscope, three-axis acceleration sensor, data acquisition and processing module, secondary power supply, optocoupler isolation input and output serial port circuit and other related structural components. The closed-loop fiber optic gyroscope is used as the core component. It mainly consists of an inertial measurement unit (IMU), a digital signal processing unit, and an organization of mechanical components. It can provide the true north azimuth for the carrier.It has the characteristics of simple structure, fast response speed, low price and good stability, etc. It can be applied to the static initial alignment of missile launch and weapon aiming in the military field, and has a wide range of applications in coal mining, oil drilling, tunnel construction, geodesy and other fields, especially in shale gas exploration and exploitation.