[OSM-dev] dropping segments (Dave Stubbs)

[Chien Nguyen Khac]

Dave Stubbs,
  <<<
If it is easy to implement routing on current osm data then why osm still
not have routing feature displaying in the web brower like google map and
yahoo map?
  
Because no-one has written one? Because the resources to provide this
aren't necessarily trivial? Because nobody with enough knowledge to do
it actually cares enough to do it? Because routing requires there be
uninterupted data from point to point which really wasn't there till
recently, making routing with osm data not very useful?
  There's a hundred reasons why there isn't one already -- you can't
suddenly claim it must be because the data model isn't optimised for
it...
>>>
   
  If making routing with current osm data stucture is not so difficult like you said then I will
wait to see how osm experts do that.
   
  Talk is easy, excurse for not doing that is also easy. Do it yourself and you will know how difficult it is.
  
<<<
With crappy lines... imagine the situation where you wish to draw a
building as a solid yellow with a brown border. You limit us to
"simple" polygons, and now we have nasty lines drawn through the
building rather than a nice solid object.
>>>
   
  I have studied a lot of mapping applications so far: Garmin, Goole map, Yahoo map... This is the  first time I heard about filling polygon with border: one solid colour within the polygon and another one colour on its borders. I guess geometry experts need to rewrite filling algorithm to meet your expectations. (For example: filling a star polygons with holes with different colours).
   
  For your information, filling complex polygons is the nightmare to render program. I guess you never write a render program.
   
<<<
If you are developing anything to do with mapping, you're gonna have
to get your geometry text book out at some point.
>>>
   
  I spend one year to study geometry and study how to zip geometry data as much as possible. For the same set of map data if Garmin can zip them down to 4MB, I can zip them even further: down to only 2MB without lossing any information. (I convert 4MB binary format of garmin map to polish format and zip that polish format to 2MB of my binary format).

  I believe I have enough knowlegde in geometry but I still feel it is difficult to use 
osm data. May be I need to wait for you to write a geometry text book on how to use osm data.
   
  <<<
My answer to this is fairly simple: so far the effort involved in
removing segments has clearly outweighed any benefits to be gained. I
say clearly because so far people have only ever talked about it.
  TBH planet isn't *that* big, and doesn't take *that* long to process
given how much information it contains. I'm sure this will become more
of a need as time passes.
>>>
   
  It does not take that long to process because you use database (MySQL...)
If you do not use database, just use plannet.osm text file and you try to clip a region (for example london city), you will know how long it will take.
   
  Regards,
   
   

       
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