Efficient evaluation of shortest travel-time path queries through spatial mashups

Abstract

In the real world, the route/path with the shortest travel time in a road network is more meaningful than that with the shortest network distance for location-based services (LBS). However, not every LBS provider has adequate resources to compute/estimate travel time for routes by themselves. A cost-effective way for LBS providers to estimate travel time for routes is to issue external route requests to Web mapping services (e.g., Google Maps, Bing Maps, and MapQuest Maps). Due to the high cost of processing such external route requests and the usage limits of Web mapping services, we take the advantage of direction sharing, parallel requesting and waypoints supported by Web mapping services to reduce the number of external route requests and the query response time for shortest travel-time route queries in this paper. We first give the definition of sharing ability to reflect the possibility of sharing the direction information of a route with others, and find out the queries that their query routes are independent with each other for parallel processing. Then, we model the problem of selecting the optimal waypoints for an external route request as finding the longest simple path in a weighted complete digraph. As it is a MAX SNP-hard problem, we propose a greedy algorithm with performance guarantee to find the best set of waypoints in an external route request. We evaluate the performance of our approach using a real Web mapping service, a real road network, real and synthetic data sets. Experimental results show the efficiency, scalability, and applicability of our approach.

The Distribution Pattern of the Railway Network in China at the County Level

“…(2) based on the location of the county center and railway station, the railway network proximity was used to reflect the convenience of the county with respect to other counties, the higher the proximity, the better the traffic conditions, the higher the support for regional development, and the greater the potential for external connection [31,32]; (3) based on the train frequency data, the shortest travel time was used to reflect the accessibility of the railway network, and the train frequency data also reflected the external service capacity of each railway station. In China, the railway is the main mode of transportation for medium-and long-distance passenger transportation, and the shortest travel time directly reflects the importance and connectivity of the county in the national railway network [33,34]; (4) the above indicators combine social and economic factors, such as population, GDP, gross industrial value above designated size, and fixed asset investment, to depict the pattern of the overall railway network distribution.…”

Leveraging wireless broadband to improve police land mobile radio programming: estimating the resource impact

“…In the context of the present study, time savings for reallocated tasking can be achieved through reduced travel time for radio programming. To best estimate realistic travel time savings for NCSHP troopers, travel time was calculated using Google Maps Application Programming Interface (API) as the Google Maps API accounts for real-time traffic patterns, varying speed limits, and diverse terrain thereby accurately reflecting actual origin to destination travel times and distances (Wang and Xu 2011;Zhang et al 2017). Travel time estimates were calculated within each NCSHP troop based upon the distance between each station location within each troop to the designated radio programming location for a given troop.…”