On Sun, Aug 15, 2010 at 1:11 PM, Tyler Gunn <ty...@egunn.com> wrote: > The one that I'm somewhat mixed on is the classification of all the minor > roads in rural MB; Canvec has all the all the gray roads in the example > link above listed as "tertiary". Given that I know these roads to be > nothing more than dirt/gravel roads between farm properties I have > downgraded the lot of them to highway=unclassified.
There are a number of reasons why the rural road grid should be tagged as tertiary in my mind. First off the descriptors used in the OSM features pages describe the system of roads found in the UK primarily. The UK is significantly smaller in size than Canada, and the road network found in that country varies considerably from that which can be found in most of Canada. With that in mind we have to interpolate. Unclassified roads used to access a farmyard in the UK might be considered a driveway in Canada. So, if you put all the 1 and 2 digit roads as primary, and all the three digit roads as secondary, you come up with a fairly useful map of the main highways. In the UK, they also have 2 designations above that that would not be used in your definition. You also suggest dropping from secondary down to unclassified. Would there be any tertiary roads in Manitoba? I look at it from an overall mapping standpoint. When you look at the UK, viewing the country as a whole, you can see quite a bit of their major road network. If you were to look at Manitoba at the same zoom level with primary highways being the highest classification, Manitoba would be blank. Primary roads show up at zoom level 7, secondary at 9, tertiary and unclassified at 10, with tertiary being distinguished differently at 13, at least on the Mapnik rendering. Being able to tell which roads should be chosen to get between locations by observing the depiction of the road on the map is of primary importance to me. If you drive all of the road designations down to the low end of the scale in Canada, you end up not being able to distinguish all of the various low grade trails and tracks from each other. In Alberta, we have the provincial road grid generally defined as tertiary. That being the road grid that is laid out along the township grid system, with Range Roads every mile going east/west, and Township Roads every 2 miles going north/south. Roads of lesser importance, and subsequently lower quality (narrower, lower grade pavement) are tagged as unclassified or residential. These roads would include subdivisions. http://www.openstreetmap.org/?lat=53.5202&lon=-113.1563&zoom=13&layers=M The depiction of these roads allows the viewer to make decisions based on visual cues, keeping to the higher grade roads, which are designed to be collectors, rather than shortcutting through residential areas on roads not designed for higher traffic flows. A lot of this thought process is based on how things would end up being rendered, but those rendering rules are based on what type of usage these roads are designed for. I have a GPS from Italy that uses the rendering rules from Italy for depicting the map data for Canada. I have both TeleAtlas and Navteq databases for the unit. Both databases are nearly useless for trying to find a decent route anywhere. Why? Because of the difference in road density between Canada and Europe. If I zoom out far enough to see Edmonton and Fort McMurray, I see no highways. If I zoom in close enough to see highways, I can see where they go to know if I can get to my destination via the highway. The distance between towns and cities in Canada is easily a magnitude greater than in Europe. Cities in Europe can be minutes apart, whereas they are generally hours apart in Canada. Have a poke around Alberta where a great deal of the road grid has been imported from GeoBase, and see what you think of how the road network import looks. We need to be consistent on a national basis... James VE6SRV _______________________________________________ Talk-ca mailing list Talk-ca@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ca
