Rob Nickerson <rob.j.nicker...@gmail.com> writes: > I'm not sure I get your point about "hint for router" versus "aid for > navigation". I suspect this may stem from the don't tag for the renderer > rule. If we look at the end use case the aim is to get a routing engine > that provides an optimal route with user friendly route instructions. I > can't believe this is an easy tag and as such I would expect the routing > developers to be raising issues they cannot solve via code alone. This is > one area where I would like my SatNav not to spew redundant instructions.
[not all directed at you of course] I think the text of the rejected proposal could have been written better. I think declaring this a hint for the router is not really the right characterization and led to trouble. We're talking about encoding facts about the world that are useful for multiple purposes. Also, "don't tag for the renderer" is about not putting wrong tags in because some renderer will make it look how you want. Describing something accurately so that it can be rendered is totally ok, and the main thing we do. What's really going on is that on the ground, it is (often) clear to a driver what "continuing on this road" means, vs "turning". This can be because of signs, or because of subtle geometry of curb cuts, or the widths of the continue vs turn roads, or various other clues. Somtimes, many of these clues can't be figured out from aerials, and certainly not From road vectors. So it makes sense to have a way to tag this so that the map data captures this on-the-ground truth. Often it's obvious from the geometry (and the obvious answer is right), and those cases don't need tags. I think for now we should avoid getting into rules about when it's not needed, and be ok with people adding the tags if they think it's confusing. I view this as similar to turn restrictions, except that instead of telling you what you can't do, it's documenting what it means to not turn. I would suggest something like "turn_description=straight", or maybe =none, to be used on the from/to ways at any junction where the look-at-the-map-and-obvious-guess answer isn't right. They should be directional because perception is going to be different, and sometimes you'll need both. There's a further question about whether routers should announce. I'd say that if the road turns 90 degrees, it should, but it should say "turn left to stay on Route 2" rather than nothing. I guess this is another wrinkle in tagging, and again is a fact about the world more than a router kludge. So I come down to turn_description=straight (road continues, obvious to driver) turn_description=stay_on_road (road continues, not obvious to driver)
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