GPS World, July 2015

Software Hardware Integration PERSONAL NAVIGATION G PS provides an accurate and reliable positioning timing service for pedestrian application in open field environments Unfortunately its positioning performance in urban areas still has a lot of room for improvement due to signal blockages and reflections caused by tall buildings The signal reflections can be divided into multipath and non line of sight NLOS effects Recently use of 3D building models as aiding information to mitigate or exclude multipath and NLOS effects has become a promising area of study At first researchers used the 3D map model to simulate multipath effects to assess the single reflection environment of a city Subsequently the metric of NLOS signal exclusion using an elevation enhanced map extracted from a 3D map was developed and tested using real vehicular data An extended idea of identifying NLOS signals using an infrared camera onboard a vehicle has been suggested The potential of using a dynamic 3D map to design a multipath exclusion filter for a vehicle based tightly coupled GPS INS integration system has also been studied A forecast satellite visibility based on a 3D urban model to exclude NLOS signals in urban areas was developed The research approaches outlined FIGURE 2 The construction of the 3D building map from a 2D map and DSM above seek to exclude the NLOS signal however the exclusion is very likely to cause a horizontal dilution of precision distortion scenario due to the blockage of buildings along the two sides of streets In other words the lateral cross direction positioning error would be much larger than that of the along track direction Therefore approaches applying multipath and NLOS signals as measurements become essential One of the most common methods the shadow matching method uses 3D building models to predict satellite visibility and compare it with measured satellite visibility to improve the cross street positioning accuracy A multipath and NLOS delay estimation based on softwaredefined radio and a 3D surface model based on a particle filter was proposed and tested in a static experiment in the Shinjuku area of Tokyo The research team of The University of Tokyo developed a particle filterbased positioning method using a 3D map to rectify the positioning result of commercial GPS single frequency receiver for pedestrian applications An evaluation of the QZSS L1 submeter class augmentation with integrity function L1 SAIF correction to the proposed pedestrian positioning method was also discussed in an earlier paper by the authors of this article However satellite visibility in the urban canyon using only GPS and QZSS would not be enough for this proposed method The use of emerging multi GNSS encompassing GLONASS Galileo and BeiDou could furnish a potential solution to the lack of visible satellites for this method This article assess the performance of the proposed pedestrian positioning method using GPS GLONASS and QZSS Building Models Construction Our work established a 3D building model by a 2D map that contained building location and height information of buildings from 3D point clouds data The Fundamental Geospatial Data FGD of Japan which provided by Japan geospatial information authority is open to the Japanese public This FGD data is employed as 2D geographic information system GIS data Thus the layouts and positions of every building on the map could be obtained from the 2D GIS data In this article the 3D digital surface model DSM data is provided by Aero Asahi Corporation FIGURE 2 shows the process of constructing the 3D building model used here This process first extracts the coordinates of every building corner from FGD as shown in the left of Figure 2 Then the 2D map is integrated with the height data from DSM The right of www gpsworld com July 2015 GPS World 37