[Talk-ca] Simplifying CanVec imports

[Adam Dunn]

Does simplifying like this cause issues where one feature joins up
with another feature? I'm assuming that JOSM won't move end nodes of
ways during simplification, so rivers connecting to lakes should be
okay, but what about places where there is a common node in the middle
of a way? Are there instances of this in Canvec, or does the Canvec
conversion process always split ways where there are nodes common to
more than one object?

If you simplify ways today, how will that affect imports in the
future, when the next version of Canvec comes out?

Adam

On Sun, Feb 13, 2011 at 8:45 AM, Daniel Begin <jfd553 at hotmail.com> wrote:
> Hi Samuel,
>
>
>
> It might be a good idea to simplify some features before importing.  It is
> not necessary for all features, and the feature's node density usually
> varies by provinces/theme.  In BC, hydro network is really dense as you
> already figured out. In Quebec, the new road network often needs to by
> simplified.
>
>
>
> I would say just do it if it is required for the tile/theme you are
> importing
>
>
>
> Daniel
>
>
>
> ________________________________
>
> From: Samuel Longiaru [mailto:longiaru at shaw.ca]
> Sent: February-11-11 10:38
> To: talk-ca at openstreetmap.org
> Subject: [Talk-ca] Simplifying CanVec imports
>
>
>
> Good Morning Everyone,
>
> For the past couple of weeks I have been importing CanVec data into an area
> southwest of Kamloops.  There was very little (if any) existing OSM data in
> the area.  I've gotten into a bit of a rhythm, merging and stitching all of
> 92I07 and about half of 92I10 but started becoming concerned about the high
> data density, particularly associated with streams in the area.  Most import
> files at the level of 92 I 07.0.0 for example, are runnning 10-15k nodes.
> At that rate, that is somewhat near 200,000 nodes for an area at the level
> of 92I07.  Yikes!  I guess the question in my mind is just how many data do
> we want to import at this level and what are the practical implications for
> server processing and overload.  I expect that this level would be fairly
> consistent across most of Western Canada. Even now, I haven't been able to
> call up a complete map in the openstreet.org view tab for the past 4 or 5
> days... 25-50% of the map being covered with "... more OSM coming soon"
> tiles.
>
> I looked at the Simplify Way function in JOSM and applying it to just the
> water data, have been able to eliminate 5-8k nodes from each file, thereby
> cutting the data in nearly half.  I really don't see any significant
> degradation in the map quality as a result.  Without simplifying, the data
> nodes in some places are incredibly (and undeservedly ) dense.  The only
> discussion I've been able to find on the simplify tool is some rather old
> discussion that took place during development.
>
> So just wondering if simplifying these data is a reasonable approach.  Right
> now, I am going back to the imported areas, calling them up from OSM,
> simplifying the water, and re-uploading the simplified data.  In the future,
> I will just simplify in JOSM before uploading the file in the first place.
> Anyway, does anyone have any issues with my approach here?  Is it worth
> simplifying  or am I being overly concerned about data density and its
> longer term implications?
>
> Thanks,
>
> Sam Longiaru
> Kamloops, BC
>
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