iOS based speed estimation for the video car recorder system

Recently, APPs (applications for intelligent mobile devices) about car recorder systems have been proposed for various mobile OS. Due to the numbers of APPs in the iOS is more than that of others OS, our car video recorder system is built on iOS. In addition, the objective-c programming language is employed to code APPs in the Xcode. Usually, the iOS mobile devices (e.g. iPhone) are equipped with GPS and camera. Hence, we only need to design software on the integration and links so as to replace the traditional tachograph. Basically, the intelligent mobile device has three types of positioning methods: built-in GPS, telecommunication base-station triangulation positioning method and Wi-Fi base-station positioning method. Although the user´s position can be quickly located, it can not provide an accurately location for user when the positioning signal are hardly received. Besides, the speed data provided by the positioning methods may easily be affected by disturbances. It should be noted that iPhone usually cannot provide an accurate car´s speed. In this study, a corrected speed method for the intelligent video car recorder is proposed. In the corrected speed method, the car speed in iPhone is corrected by the linear regression method. In our experience, the proposed method can improve the accuracy of the car speed estimation in iPhone.