[Talk-ca] Importing Canvec data, but causing huge issues

Adam Dunn dunnadam at gmail.com
Sat Apr 2 19:21:32 BST 2011


I don't have or use Merkaartor, I'm a JOSM fellow. For reference, the
lake that you pointed to is in 083H07.1.2
[ftp://ftp2.cits.rncan.gc.ca/osm/pub/083/H/083H07.zip]

You're right in that there's nothing wrong with the Canvec data. Well,
it does have two duped ways, which could be reduced, but that's not
that big a deal. The original data has singular nodes (non-duplicate),
and two ways that are duplicates, where one way is a simple
natural=water, and the other way is an inner member of a natural=wood
relation.

Somehow you've managed to upload:
Triply-duplicated nodes.
Three duplicated ways of which:
  One is the original natural=water polygon
  The two other ways are both inner members of 16 identical
natural=wood relations. That is to say, you've sexdecupled the
natural=wood relation.

Not being a Merkaartor person, I can't say exactly what caused this. I
would guess  that the triple-duplicate nodes would be caused by
copy-pasting things individually (you copy paste the water, which will
create one set of nodes, then you copy paste woods which will create
another set of nodes, which are dupes of the first set). I'm not sure
about the sexdecuply duplicated relation or the doubly duplicated wood
inner ways.

Does Merkaartor have a validation step or plugin (like JOSM has validator)?

For how long have these errors been uploaded (how many tiles uploaded
are like this)?

Adam

On Sat, Apr 2, 2011 at 10:01 AM, James Ewen <ve6srv at gmail.com> wrote:
> Can anyone shed some light on why I am causing problems when importing
> CanVec data?
>
> I am using Merkaartor to import the CanVec OSM tiles located here:
>
> ftp://ftp2.cits.rncan.gc.ca/osm/pub
>
> I used find to select the desired entity (natural:water), and the copy
> and paste the features. I then upload the features to the OSM server.
>
> However, this process appears to be creating duplicate nodes like crazy.
>
> http://matt.dev.openstreetmap.org/dupe_nodes/about.html
>
> If you look at some of the uploaded information, you can see that
> there are multiple copies of some nodes and ways, and some have
> multiple duplicate tags included.
>
> Here's a tight zoom on a lake:
>
> http://www.openstreetmap.org/?lat=53.485292&lon=-112.80943&zoom=18&layers=M
>
> If you add the data overlay, you can see that there are multiple ways
> describing this lake.
>
> If you find the multipolygon for natural:wood, you'll see that it has
> 16 tags indicating that it is part of a relation as inner...
>
> If the source of this problem the CanVec data itself (unlikely),
> something Merkaartor is doing (unlikely), or something the wingnut at
> the keyboard is doing (likely).
>
> Whatever the source, what can I do to fix the problem short of
> stopping working on CanVec to OSM imports?
>
> James
> VE6SRV
>
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>



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