Boots – shoes – and leggings
Patent
1989-08-24
1991-01-08
Black, Thomas G.
Boots, shoes, and leggings
340995, G06F 1550
Patent
active
049841688
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method and a system for determining a route between a starting point and a destination.
BACKGROUND
An autonomous direction-finding and navigation system known as EVA (electronic navigator for drivers) for land vehicles is in development. Calculation of an optimal route from an arbitrary starting point to a freely selectable destination or target is based on a road map stored digitally in memory. The greater the distance between the destination and the starting point, the more manifold the possible ways of reaching it by using the memorized road map. These routes are not all equally good; the optimal route must therefore be ascertained by calculation. The computing time needed for extensive computations may mean that the results are not available to the driver in time; he may already have missed a fork in the road or an intersection where he should have turned.
THE INVENTION
It an object of the invention to devise a method and a system for determining a route between a starting point and a destination that ascertains the optimal route quickly and reliably, even for extensive road systems.
Briefly, a computer is coupled to a read-only memory which, in accordance with a feature of the invention, is subdivided to store the maps of regions in at least two levels in which one of the levels contains a plurality of smaller subregions, and the resolution of the maps is to be such that the grid density is fine; and the resolution of other levels become coarser and coarser. The route is then plotted by determining first if the starting point and the destination or target are on the same lowest level map; if so, the route can be plotted directly based on the memory within this lowest level subregion. For a longer trip, the starting point and destination will not be on the same sublevel. The computer then transfers into the computer working memory only those maps from the next higher level memory which have transitions to the fine, lower level maps in which the starting point and destination are located. Thus, only selected portions of coarser-and-coarser road maps need be transferred into the operating memory of the computer, thus substantially decreasing computation time.
The invention is based on the consideration that in the vicinity of the starting point and destination, traffic is carried over secondary roads, while the longer distances are covered over highways and superhighways. Highways and superhighways carry the combined streams of traffic from various regions. In a relatively large region, if only the roads carrying long-distance traffic are taken into account, the resultant road map has a coarser grid density, so there are fewer options for variation over different roads and less computation time for the on-board computer is therefore required.
Dividing the road map into levels is suitably done in such a way that each region offset approximately the same number of options for variation in finding the route segment to take, and thus occupies the same number of memory locations in the computer and correspondingly requires the same computing time. Geographical characteristics can also be considered, and particularly if a plurality of different transitions or connections exist between the several regions. In joining several regions of a lower or lower-ranking level into a high-level region, once again these criteria are employed. In this way, several levels can be formed with make it possible to work out a route even over international borders.
It is particularly suitable if the grids are formed from roads and hubs, with the hubs in the lower level representing forks or intersections and those in the higher level representing subregions of the lower or next-lower level. In this way, the same systematics can be continued at the transition from one level to another, and the route determination can be performed by the same algorithm. Electrical resistance values are suitably, assigned to the roads and hubs; they are for instance set low for superhighways, b
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patent: 4760531 (1988-07-01), Yasui et al.
patent: 4812980 (1989-03-01), Yamada et al.
Bosch Technische Berichte, vol. 8, No. 1/2, 1986, pp. 7-14.
AFIPS Conf. Proc. National Computer Conference, 9-12; Jul. 1984, p. 6960706.
Funkschau, Issue 4, Feb. 1985, (Munich, Fed. Rep. Germany), pp. 33-36.
Neukrichner Ernst-Peter
Schlogl Dietmar
Black Thomas G.
Robert & Bosch GmbH
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