v4 - in the absence of a through_route relation, don't be fooled into thinking that a side road is the continuing road when it has the same name as the continuing road. -------------------- v3 - bug fixes: now ignores through_route relations if the junction is outside of the tile's bounding box should no longer think that ways that have been split do not start or end at the junction. -------------------- v2 - no longer requires the node to have role "junction" This patch also includes two other changes to the heading adjustment code: When matching arcs, as a last resort, match road class and speed. If at a node, an outgoing arc cannot be matched to an incoming arc by possiblySameRoad(), try to find a single outgoing arc that has the same road class and speed as the incoming arc and use that. and: When adjusting turn headings apply all relevant adjustments. Previously, if a heading needed adjusting because the delta from the outgoing arc was too small, it did not then consider whether the delta from the incoming arc was too small also. Now, it considers both cases and adjusts the heading as appropriate. So please test even if you are not adding any through_route relations and if you see any notable changes (good or bad) please say. -------------------- This new relation (type through_route) specifies which 2 ways are the "through route" at a junction. The relation requires 2 ways (no role required) and a node with role = junction. It should only be used at those junctions where the through route cannot be reliably inferred from the ways' names and/or refs. Here's an example from my local town: | 1 | / | / |/ A | | | | B /| / | / | 2 | The vertical road is the "through route", i.e. you can drive from one end to the other without crossing any white lines. But, from point 1 to point 2 is a B road so ways 1-A, A-B, and B-2 all have some ref, say, B1234. Without the through_route relation, mkgmap assumes (erroneously) that the through route is 1-2 because all of the ways in that route have the ref B1234. By adding 2 through_route relations (one at A and the other at B), mkgmap is informed of the real through route and will take that into account when adjusting the turn headings. The end result is that the quality of the routing directions is improved (we hope). In this example, we need to have 2 relations because the B road joins/leaves the through route at two places. So if you know of any junctions that would benefit from this relation, please add it to the map data and try this patch to see if it improves the routing instructions. Mark