Research On Fish-eye Image Aiding Low-cost GPS Urban Area Positioning

As the demand for a series of applications that rely on high-precision positioning services has increased dramatically in urban environments,how to improve the positioning performance with low-cost GNSS positioning terminals in urban areas has become a hot research topic.In urban areas with dense buildings and complex environments,multipath effects including multipath interference and non-line-of-sight(NLOS)signals can seriously affect the performance of low-cost terminals.In order to achieve better performance of low-cost terminals in urban area positioning,this paper takes GPS and smartphone terminal equipped with dual-frequency positioning chip as research object,and conducts the following researches around the processing method of multipath effects:1? Vision-based NLOS signal detection method is studied.In this paper,a low-cost mobile phone fish-eye lens is used to obtain the sky-plot of the location point,to know the obstacles of the surroundings.A low-cost and high-integration data acquisition mode is explored.K-means obstacles segmentation algorithm based on geodesic reconstruction by dilation is proposed.This strategy first uses geodesic reconstruction by dilation method to simplify the local information of images,and then uses K-means clustering algorithm to segment the images.Through experiments,it is verified that this strategy can effectively segment obstacles in the images obtained by the low-cost fish-eye lens,and the purpose of NLOS signal detection by combining fish-eye image is achieved.2? The suppression effect of weighting models on multipath effect is studied.Three classic weighting models are introduced,and several experiments are performed to analyze the performance of different models on improving positioning accuracy.Based on the comprehensive weighting model that has better results,the effect of NLOS signal weight reduction strategy on the improvement of positioning results is discussed.3? The correction algorithm of NLOS signal is studied.Firstly,Urban Trench algorithm based on three-dimensional map is introduced.In order to solve the problem that the ratio P of the distance between the receiver and the left building to the total lane width needs to be estimated in advance,a FE-Urban Trench algorithm is proposed.This algorithm combines the comprehensive weighting model,and uses the sky-plot obtained from the fish-eye lens to assist in the estimation of P value,thereby correcting the NLOS signal and improving the positioning accuracy in the cross-street direction.After several experiments,this algorithm can effectively ameliorate the multipath effect in urban areas.4? The effect of L1L5 dual-frequency fusion on improving the positioning performance of smartphone terminals is studied.Based on FE-Urban Trench algorithm,combined with the L5 band data that own better anti-multipath performance in GPS,a FE-Urban Trench algorithm based on dual-frequency fusion and L5 weight lifting is proposed.Compared with the traditional pseudorange correction algorithm,this one adds the consideration on suppression of multipath interference.Through static experiments and dynamic experiments,the improvement of the positioning accuracy of the algorithm is verified,and conclusion is drawn that the dual-frequency fusion strategy can effectively suppress the urban multipath effect.