Causes and Countermeasures of Signal Drift Problems in Vehicle GPS
When the current GPS voice navigation products are used for road testing, when the speed exceeds 40 kilometers, the signal reception will more or less "drift". In this regard, Zhou Yang believes that it is normal, because the positioning accuracy of the existing GPS at rest is only 5 to 20 meters, which causes drifting during driving, which is more obvious when the vehicle speed is faster, and time, location, climate, etc. will affect GPS. Positioning accuracy. But the main reason is also the processing power of the hardware (especially the processing speed of the CPU and GPS algorithm) and the convenience of navigation software.
In this regard, some netizens pointed out that before solving the problem, it is necessary to distinguish between software and hardware. When the weather is fine, compare the GPS output signal detected when the car is driving at high speed with the data at the stop to get the actual data of "drift". In terms of problem solving, he believes that GPS positioning accuracy is basically inevitable under the existing conditions, the processing speed of hardware has been basically solved, and the running speed of software is currently far from enough; as for the accuracy and detail of the map, Basically meet the needs of use, but it is not enough and needs to be further improved. Another netizen pointed out that because this problem is mainly caused by the Doppler effect, a high-dynamic GPS receiver must be used on the high-speed moving body.
Start with the software to solve the problem of voice lag
Another problem that GSP voice navigation products often encounter when vehicles move 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 voice processing system is slightly slower.
In this regard, Zhou Yang also analyzed that the software is still far from the optimal use. A program, 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 solution can only be advance notice and multiple reminders, thereby reducing the error of a single forecast.
Realize power-off storage of vehicle GPS data
The location of the car while driving, and the relevant information such as the time and place of parking are all data that the GPS needs to store. Designers generally use power-off storage when processing this information, will this have an adverse effect on the entire system?
In this regard, Liu Lijiang pointed out that for GPS receivers, the relevant ephemeris data can be stored within a few hours after power-off, can it be fast when powered on? ? Satellite, thus achieving the effect of a hot start that works normally within a few seconds. The longitude and latitude data of the car at each moment, as well as the parking time and location and other related information are generally stored in the system memory outside the GPS receiver, because this is the target information. If the power failure is lost, the system generally has to obtain 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 during design, which will not affect the entire system.
Anti-jamming design of handheld GPS
As a radio frequency of 1.575GHz, the interference problem is much more serious than that of 800-900MHz mobile phones. Li Jin believes that the following points should be noted: 1) The bypass of the power supply part; 2) The high-speed circuit is away from the radio frequency part; 3) The microstrip transmission line of the radio frequency is as short as possible; 4) The radio frequency part is shielded; 5) The antenna The tail lobe, side lobe, and even the main lobe of low angle are shielded and protected; 6) When necessary, soft shielding materials can be used for split-type shielding.
Zhou Yang made his point of view from another angle. He believes that it is possible to start from the three aspects of device level, motherboard level, and machine level. The motherboard level is the top priority. The solutions include: adding the high-frequency part to the shield, and separating the high-frequency part into separate board levels. In terms of 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 during the assembly stage, and an isolation board is added.
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