engleski

Validation of speed profiles using FMCW radars

Most modern vehicles are equipped with some kind of navigation system which uses GNSS combined with digital maps to provide as accurate as possible real-time positioning and navigation. Navigation in urban areas presents a rather difficult task because optimal route is not unique and can vary, depending on traffic conditions which change during the day as well as in case of unexpected scenarios, like traffic accidents. To allow optimal route planning, providers of navigation systems rely on calculating of speed profiles from GPS traces gathered from users which allowed that option in their navigation systems. Speed profiles are calculated estimates of average speed which can be achieved on a specific road segment during one day. Systems which have possibility to send data using mobile networks are usually mobile phones, while on-boards navigation devices mostly do not have that possibility. This leads to a problem of having technology which is not used to its full potential. Some providers of free navigation solutions, like Google or Here, rely on gathering data from devices which have mobile network connection to provide more accurate estimation of travel time. As a cost function user can specify travel time, which changes throughout a day or in case of an unexpected traffic jam, and navigation system tries to predict the best route for given input parameters. Speed profiles, on the other hand, try to predict a priori scenario which is fixed to a certain period of the day, to specific day of the week and specific part of the year. This approach gives logistic and transport companies a much better tool for route-prediction but it can also help private users when traveling from point A to point B in an unknown city during rush hours. To solve time dependent vehicle routing problem one must be able to gather a large amount of data from vehicles equipped with satellite navigation system and use them to calculate speed profiles for certain road segments. Since gathered GPS traces collected for the same road segment have errors in position due to inaccuracy in GPS positioning, we have used Frequency Modulated Continuous Wave (FMCW) radars to verify the data collected using GPS with actual measurements on road segments. For that purpose we have installed four of such detectors at four different locations and collected vehicle data (speed, length) for more than 1.5 million vehicles. Speed profiles calculated from GPS traces for these locations were compared with radar measurements and from them we are able to conclude that usage of GPS data is accurate enough to calculate the correct speed profile, given that we have enough of individual traces at our disposal.

GNSS; Speed profiles; Vehicle routing; FMCW radars

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