Are these differences errors or there are formal reason for them? Look at the extract in the permalink: https://www.openstreetmap.org/?lat=49.0032&lon=-120.498&zoom=12&layers=M As an experienced mapper, I can understand the sharp cut on the white holes, displaced country border... but I dont understan the color differences for the (obviously) same area object types (light and dark green), the horizontal/vertical tile/grid lines, the very weak contrast between the light-green and light-blue... As I undestand, the SlippyMap is OSM's reference map and should be (among) the best maps created on the most recen/valid OSM source data. asked 12 May '13, 10:59  sanser |
One Answer:
The darker green comes from a landuse=forest relation and the lighter green from a natural=wood relation. Additionally there is a boundary=national_park / leisure=nature_reserve combination rendered as an area with many "NR" labels and to the west there is a boundary=national_park without the leisure=nature_reserve tag but with a leisure=park tag resulting in an even lighter green. Somewhat confusing but that's what you get if you want to render many different tags. answered 12 May '13, 12:22  scai ♦ edited 12 May '13, 20:13 |
This comes back to the conflicting interpretations of landuse=forest vs natural=wood. In this case they really should be tagged the same on each side of the border, but different mappers follow different conventions.
I keep pushing for the "landuse=forest is for forestry activity" interpretation, but some people use another interpreation, many people dont know/care, and many areas are hard to judge either way. Sigh...
It's worse than you think: a lot of US forests are just land which is designated National Forest and run by the Forest Service. In many cases there is nary a tree in sight, although this area is mainly forested, but there are gaps http://mc.bbbike.org/mc/?lon=-121.78925&lat=48.93702&zoom=15&num=4&mt0=mapnik-german&mt1=bing-satellite&mt2=hike_bike&mt3=mapquest-satellite. Note the miasalignment of US/Canadian border. North Cascades National Park was also tagged leisure=park (I removed it).