Causes and Countermeasures of Signal Drift Problem in Car GPS
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At present, when GPS navigation products are used for road test, when the speed exceeds 40 kilometers, the signal reception will be more or less "drift". In this regard, Zhou Yang believes that it is normal, because the positioning accuracy of the existing GPS static state is only 5 to 20 meters, which makes the drift phenomenon during driving, the speed is more obvious when the speed is faster, and the time, place, climate, etc. will affect GPS. Positioning accuracy. But the main reason is the processing power of the hardware (especially the CPU processing speed and GPS algorithm) and the convenience of navigation software.
In this regard, some netizens pointed out that before solving this problem, the first thing to distinguish is software or hardware. When the weather is fine, the GPS output signal detected when the car is driving at a high speed is compared with the data at the time of stopping, and the actual data of "drift" can be obtained. In terms of solving the problem, he believes that the GPS positioning accuracy is basically unavoidable under the existing conditions, the processing speed of the hardware has been basically solved, and the running speed of the software is still far from enough; as for the accuracy and detail of the map, Basically meet the needs of use, but not enough, to be further improved. Another netizen pointed out that since this problem is mainly caused by the Doppler effect, a high dynamic GPS receiver must be used on high-speed mobile bodies.
Start with software to solve the problem of voice lag
Another problem that GSP voice navigation products often encounter when the car moves at high speed is the problem of voice lag. In this regard, Li Jin pointed out that there are two possibilities, one is that the positioning itself has errors, and the other is that the speech processing system is slightly slower.
In this regard, Zhou Yang also analyzed that the software is still far from being optimized for use. A program and different writing methods greatly affect the total processing time of the program. Therefore, in terms of voice navigation, due to software problems, there is indeed a lag phenomenon. The existing solutions can only be early notice and multiple reminders, thus reducing the error of a single forecast.
Realize power-down storage of car GPS data
The location of the car when it is driving, as well as the time and place of parking, are all the data that GPS needs to store. Designers generally use power-down storage when processing this information. Will this adversely affect the entire system?
In this regard, Liu Yujiang pointed out that for GPS receivers, the relevant ephemeris data can be stored in a few hours after power failure, which can be fast when powering up? ? The satellite, thus achieving the effect of a hot start for normal operation within a few seconds. The longitude and latitude data of the car at each moment, as well as the time and place of parking, are generally stored in the system memory outside the GPS receiver, as this is the target information. If the power loss is lost, the system generally needs to re-acquire new latitude and longitude and other related information from the GPS receiver, and then calculate the current position information of the car. For this type of information, it is best to implement power-down storage at design time, which does not affect the entire system.
Handheld GPS anti-jamming design
As the 1.575GHz radio frequency, the interference problem is much more serious than the 800-900MHz mobile phone. Li Jin believes that the following points should be noted: 1) bypass of the power supply section; 2) high-speed circuit away from the radio frequency part; 3) radio frequency microstrip transmission line as short as possible; 4) shielding the radio frequency part; 5) The tail flap, side lobes, and even the low-angle main lobe are shielded; 6) Flexible shielding materials can be used for shielded shielding if necessary.
Zhou Yang put forward his own point of view from another angle. He believes that it can be started from the device level, the motherboard level, and the whole machine level. Among them, the motherboard level is the most important. The solution includes: adding the shield to the high frequency part and separating the high frequency part into independent board level. In the whole machine, you can refer to the following two strategies: the whole machine becomes a common potential body, and the interference problem between each board level and components is considered in the assembly stage, and the isolation board is added.
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