[talk-au] Optimising map rendering for recreational use

David Bannon dbannon at internode.on.net
Thu Nov 1 09:16:39 GMT 2012

Li, another complication worth thinking about. In theory, when we map
a road, the highway tag needs to relate to the purpose of the road
rather than the condition. This is a topic that has been under
discussion for the last week or so. And renderers really only seem to
be interested in the highway tag, ignore tags such as 4wd_only and
tracktype (for other than highway=track).

So, for example, roads such as the Tanami track or Plenty Highway are
technically, primary roads. And therefore rendered at quite a broad
zoom level. I got all upset about this as I am worried that
potentially visitors see a nice thick line and assume its a nice road.
(In fact they are great roads but not for the ill equipped!).

I have been pushing the idea if we are to stick to the politically
correct idea that highway is about purpose and not condition, then we
need a reliable way to warn people reading the maps AND importantly,
people building rendering engines what the condition might be.

Please see the discussion page on
http://wiki.openstreetmap.org/wiki/Australian_Tagging_Guidelines and

I have suggested extending tracktype to, a) have additional levels of
difficulty and b) clarify that this grading really does apply to all
roads, not just highway=track

I do think that this might be a better way to achieve what you want
too. But the real issue is the mainstream renders and the routers
won't think about it unless its widely adopted and used. As they say
in the ALP, disunity is death !


----- Original Message -----
From: "Li Xia" 
Sent:Thu, 1 Nov 2012 15:01:11 +1100
Subject:[talk-au] Optimising map rendering for recreational use

 Hey everyone, have an idea about map rendering and want to get your
 One of the challenges is in rendering a useful map for recreational
use is displaying roads, tracks, trails and to some degree water lines
at appropriate zoom levels in more remote regions where the density is
lower compared with urban regions. 
  In my opinion, most map service online services or offline vector
engine experience the same issue. Here are some illustrations of the
issue, by comparing Google / OSM / Raster map of the same region:

 Google [1]  
 OSM [2] 
 Raster map [3] 
 As you can clearly see, at that zoom level, there's no deal on either
OSM or Google maps, where as the raster map is useful. yes you can
zoom in on Google or OSM, but with a smaller viewing port, orientation
is more difficult and you loose that overview which is try handy for
trip planning. 
 By using a tag specific for rendering purposes, this issue can be
overcome. Rendering engines can take advantage of these tags to
"optimise" rendering of various regions. 
 The tags are fairly self explanatory. By tagging a road with
render_as:trunk, this feature can be rendered at the same zoom level
as a trench road. Each class of road will have it's own tag so if a
highway:territory should be rendered at the same zoom level as a
primary, then tag render_as:tertiary. 
 What do you guys think? 


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