[Talk-ca] Large polygons in JOSM

Daniel Begin jfd553 at hotmail.com
Thu Sep 18 11:47:00 UTC 2014

Oups, forgot your second point…


About motivation to clean the north, I think a specialized bot could remove duplicated water/wooded area geometries. About merging all these tiles, it would mean having a multipolygon covering about half of the country with hundreds of thousands of hole in it…   I am almost certain that merging all of them would not be a good idea.


Anyone could comment about the consequences of merging all these tiles?



From: Daniel Begin [mailto:jfd553 at hotmail.com] 
Sent: September-18-14 06:46
To: 'Stewart C. Russell'; talk-ca at openstreetmap.org
Subject: Re: [Talk-ca] Large polygons in JOSM


Bonjour Stewart,


Basically, you need to identify the lake as being a hole in the wooded area. Since both the lake and the hole are provided with Canvec data, you need either to …

-          Delete the lake and tag the hole as natural=water, or 

-          Delete the hole and add the lake as an inner component of the multipolygon.


The same sometime applies with wetlands in cases wetlands create a hole in the wooded area (you need a good imagery to see it); however, I should confess I do it only when it is not too complex ;-) 


See an example here: http://www.openstreetmap.org/#map=16/45.8514/-71.1917





From: Stewart C. Russell [mailto:scruss at gmail.com] 
Sent: September-17-14 20:46
To: talk-ca at openstreetmap.org
Subject: Re: [Talk-ca] Large polygons in JOSM


On 14-09-15 05:41 PM, Daniel Begin wrote:


About Canvec, the product often duplicates water bodies and inner polygons of wooded areas; which is not necessary where both were imported. In order to keep only the necessary geometries, I usually transfer all the tags from a waterbody to the duplicated geometry of an inner polygon and then, I delete the original - now duplicated - waterbody.


Hi Daniel,

I have to confess I don't quite follow what you're doing here. Are you leaving the waterbody defined only as the inner polygon (aka, a hole) of a landuse multipolygon? Are there any example ways you can link to that do this? 

The difficulty with the huge 'tiled' areas of the North is that few people will find the motivation needed to clean up the imports into coherent polygons.


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