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speedometer reading faster than actual speed
When the car runs at a high speed, the instrument displays 100 km / h, while the navigation displays 96 km / h, why are the two displays inconsistent? In fact, the vehicle instrument speed and navigation speed are not absolutely accurate. Both of them have a certain degree of error. For example, when walking on a curve, the navigation display speed is not accurate, because GPS can't locate a straight line and a curve.
1:Why is there an error in the navigation display speed?
Because the navigation shows a straight line, and there may be some bends in the actual driving road conditions. For example, the straight line distance is 12M, the actual distance is 15m, and the passage is completed in 5 seconds; Then the navigation speed is 2.4 meters per second, while the actual speed is 3 meters per second.
2:Is the navigation speed slower than the actual speed?
Although today's navigation is much more accurate than in the past, there must be some errors in a small range, which is difficult to eliminate.
3:Is the vehicle speed displayed on the instrument accurate?
In fact, the displayed speed of the car is also inaccurate and will be faster than the actual speed; For example, the displayed speed is 121km, which has exceeded the maximum speed limit, but the actual speed is still within 120km, and there is no overspeed; There are generally two reasons for this phenomenon. First, there is a certain error in the sensor itself to obtain various data on the car; Second, according to relevant regulations, the displayed speed must be faster than the actual speed. For example, if the speed collected by the sensor is 15km / h, the displayed speed is generally 18-20km! There are generally three sensors on the vehicle that can obtain wheel rotation data, namely the input shaft and output shaft sensors on the gearbox, and the other is esp. the vehicle speed is calculated by calculating the rotation times of the drive shaft, and the calculated results will be sent to the CAN bus and finally reflected on the vehicle instrument; However, there will be some errors in the data captured by the sensor, so it is impossible to accurately calculate the actual speed! Secondly, there are also requirements for the apparent speed at the rule level, so it will inevitably lead to the inaccuracy of the apparent speed of the car.
At the level of rules, according to the standard of automobile speedometer (gb15082-2008), the relationship between the actual speed and the apparent speed is as follows 0 ≤ indicated vehicle speed - actual vehicle speed ≤ actual vehicle speed / 10 + 4km / h. The other calculation method is that the meter displayed speed = actual speed * 1.03 + 2.5km. No matter which of the above two calculation methods is used, the calculated meter displayed speed must be higher than the actual speed
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