Vol.3 No.4 2011

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Research paper : How car navigation systems have been put into practical use (H. Ikeda et al.)−284−Synthesiology - English edition Vol.3 No.4 (2011) At first, each NAVS supplier independently began data development. Sumitomo Electric developed data for the three metropolitan regions based on detailed map data such as 1:2500 urban planning maps issued by power companies, gas companies and municipalities. This process required permissions from municipalities. Our development staff branched out and visited municipal governments to obtain permission.(2) Japan Digital Road Map Association[8]Independently-developed map data was sufficient to meet early metropolitan application requirements. As there were growing trends toward wider use of the NAVS, however, each supplier became aware that map data should not be developed separately by private businesses, spending a large number of man-hours and large expense. Accordingly, we worked on interested sectors. Our efforts led to establishing the Japan Digital Road Map Association to develop digital road maps, with the then Ministry of Construction taking the initiative. Key issues in founding the association were specifications (standardization) and members (user attraction). One major achievement was that automakers decided to cooperate in the domain of surveys and editing for the industry’s sake while leaving the domain of designing how information is displayed for the competition. Participants from the then Ministry of Construction were the Road Bureau and the Geospatial Information Authority of Japan. Although shared use of map data implied loss of differentiation, private businesses took part in the association, providing funds and member fees and sending engineers, in anticipation of cost reductions.Meanwhile, functional requirements for map data have changed with the advance of the NAVS. Simply displaying the current location, the first generation was required to ensure network accuracy. The second generation, which displayed a route to the destination, met the needs for information on regulations, such as one-way traffic, right/left turns and presence/absence of a median strip. The third generation, displaying traffic information, was required to ensure consistency with traffic jam data management units. Since then, the Digital Road Map Association has provided data to sustain the NAVS in Japan. Route navigation was achieved by combining the original map data with the no-right/left turn and other traffic regulation data administered by the police.3.4 Receiving traffic informationJapan makes optimal use of traffic networks constructed on its narrow land. Road traffic management in Japan is the most advanced in the world. Traffic jam conditions have been monitored by numerous vehicle sensors[9], image sensors and intersection-monitoring cameras installed on roads. Traffic jam information was provided to NAVS via multiple media: FM broadcasting administered by the then Ministry of Posts and Telecommunications; radio wave beacons[10] on expressways administered by the then Ministry of Construction; and optical vehicle detectors[11] (optical beacons) on general roads under the control of the National Police Agency. The Vehicle Information and Communications System[12] (VICS) Center was founded through the efforts of interested parties. Information collected at the VICS Center was sent to NAVS via each media center. This scheme enabled NAVS to obtain information on nationwide traffic jam conditions. Thanks to the efforts of involved parties from the business sector, we were able to overcome the challenge of integrating the different mediums and were able to develop a uniform format for shared data sent via radio waves.Again, data processing software was important for receiving data from the beacon. It was necessary under any display conditions for the NAVS to instantly display simple graphic data unique to a specific location, sent from a beacon, as with handling an interrupt. Receiving beacon data at times of high CPU or memory load, as when changing to a different display scale or route re-searching, resulted in heavy demands on internal processing.In providing traffic information, it was necessary to ensure correspondence among expressions of map data containing traffic jam information, data at the VICS Center, and data on onboard NAVS units. A solution was developed thanks to the efforts of interested parties. In Fig. 6, green and red arrows on the map represent uncrowded and crowded roads, respectively. In 1973, CACS envisioned coordination between onboard equipment and infrastructure. A coordinated system was finally achieved in 1996 when NAVS had become popular and VICS was established.3.5 Development of other core componentsThe NAVS was required to perform map-matching and show computation results of a route up to the destination and route navigation in real time over the map on the display. This resulted in a need for large memory, software size and computational power previously unseen with conventional onboard equipment. Semiconductor memory in the initial phase of development was far below the required level of capacity to store display and map-matching maps within the Fig. 6 Map displayed with traffic jam information(VICSセンター資料より)

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