GPS receiver can receive accurate time information to nanosecond level which can be used for timing; Broadcast ephemeris used to calculate the satellite coordinates required for positioning, with the accuracy of a few meters to dozens of meters (each satellite is different, varies from time to time); And car gps navigatorsystem information, such as satellite status.
Basic functions of car gps navigator 1) Car gps navigator positioning function: immediate positioning and timing positioning.
2) two-way call: the authorization number corresponding to the button can be set separately. When the button is pressed, the authorization number can be called and the incoming call can be answered.
3) Car gps navigator alarm function: emergency alarm, displacement alarm, overspeed alarm, crossover alarm, low power alarm, anti-theft alarm.
4) car gps navigator electronic fence: when the terminal exceeds the preset restricted area, it will automatically send an alarm message to the monitoring platform and a short message to the supervising mobile phone to send an alarm message over the area.
5) Car gps navigator remote monitoring: the monitoring number can be set. When the number is called to the terminal, the terminal will automatically answer the call, so as to achieve the monitoring effect.
6)Car gps navigator automatic sleep: the built-in vibration sensor will automatically enter the sleep state if there is no vibration within the specified time.
Three common mobile phone location data sources and analysis methods Car gps navigator and LBS base station positioning are the main sources of mobile phone positioning data. According to different mobile phone applications, they can be expressed in various forms of mobile phone data sources. The following are three common mobile phone positioning data sources and analysis methods:
1) App log file The log data in APP log files such as txt.log.ini has a certain format, and regular expressions of certain algorithms can be used to retrieve and locate the data. As shown in FIG. 2, atitude in GPS positioning data = 30.570579 is latitude, longitude = 104.063774 is longitude, and the time is 2015/7/15 17:46:20.
2)The DB database DB database is widely used in IOS and Android applications. DB database file is used to store the basic parameters required by App operation and the data needed to be saved by user Settings during operation. As shown in figure 4, open a DB database file that records location data. The loc field is location abbreviation, that is, encrypted data containing location information. The time field is Unix timestamp
3)Media files We can usually set whether to save the current position when taking photos or recording video with our mobile phone. Setting the JPG, MP4, MOV and other media file properties after saving, we can save the positioning data during shooting.
In the car gps navigator of IOS and Android, many applications will locate the current location of users, such as weather forecast, map software, social software and so on. Most of these applications use GPS and LBS base station for positioning, and of course, some others use WiFi, a-gps, gps-one and so on. Mobile location data is stored in the App's local App location, and some of it may be stored on the App cloud server. For mobile phone forensics, geographical location information is mainly extracted from local App files.