What is inertial navigation
Inertial navigation system (INS) is an autonomous navigation system that does not rely on external information or radiate external energy, but the term itself has nothing to do with GNSS(Global Navigation Satellite System) navigation.
The inertial navigation system consists of a gyroscope and an accelerometer:
1. The gyroscope has the property of pointing steadily in one direction and is not associated with the movement of the outside world.When such a device is attached to an object that is rotating in its direction, the Angle at which the object is rotating can be measured.
2. The accelerometer can measure the acceleration value of the movement of the object, and with the time record, the distance can be calculated according to S =(1/2) A *t^2.And the acceleration is changing all the time, right?So let's integrate.
Three-axis gyroscopes point to the XYZ axis in the coordinate axis respectively, and the accelerometer is added to the three axes to form the inertial navigation device.By changing the Angle of the three axes and accumulating the distance between the three axes, you can measure the three-axis position movement of the object in the three-dimensional space, that is, the three-dimensional space displacement. However, you will find that such a device can only measure the relative displacement, that is, the displacement between two certain moments in the time record.
Inertial navigation and GNSS navigation
GNSS navigation is a system that guides users to travel according to the location information provided by GPS/BD and the route planned before navigation.
As we know, GPS/BD calculates its position by receiving the signal sent by the satellite. When the satellite is blocked, the positioning equipment can not locate.Occlusion can occur in a variety of ways, such as over viaducts, tunnels, etc.At this point, the parking icon in the navigation may stop moving until the car is in an open area and you will see the space jump over.
In addition, through the relationship of speed, time and distance, the possible position can be inferred according to the speed calculated by the last satellite signal so as to continue to realize navigation.However, if the acceleration and deceleration of the vehicle vary greatly, the final presumed position will deviate greatly from the current actual position, which will bring bad experience to the user anyway.
The combined application of inertial navigation and GNSS not only solves the problem that GNSS equipment loses its navigation position in the case of star loss, but also solves the problem that simple inertial navigation equipment only has relative displacement.When the positioning accuracy of GNSS equipment decreases, the inertial navigation equipment is used to compensate and calculate the navigation position.GNSS equipment is used to compensate and calculate the position when the inertial navigation equipment accuracy decreases.
In the field of navigation, the combination of GNSS and inertial navigation can well solve the problem of positioning and driving in the sheltering environment such as tunnels, tall buildings, under Bridges or woods.However, due to the inertial navigation equipment also has its own technical shortcomings (the inertial navigation system error is mainly affected by time and temperature, and the cumulative error is easy to expand), so the long-term navigation is still very difficult.
Today, GNSS is the leading location technology in a wide range of applications, and the geospatial industry has seen impressive technological advances over the past 30 years.
