Hello,

Recently I noticed that one of the lakes in my area is not drawn properly on the standard map - no blue at all, it's marked as "meadow" or something. Shows fine in bicycle/transport/mapquest map. This is Anderson Reservoir, in the middle of the map here:

http://www.openstreetmap.org/?lat=37.1694&lon=-121.6205&zoom=14&layers=M

I checked things with JOSM - the lake seems to be a closed polygon, clockwise direction, looks fine to me. There are some complex overlapping polygons that I guess cause the problem, but I don't dare attempt this complex an edit without understanding the problem first. Can somebody more experienced in OSM matters take a look?

Regards,

  • Alex

asked 21 Mar '13, 17:45

Alexander%20Avtanski's gravatar image

Alexander Av...
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accept rate: 0%

1

Thanks everybody.

I'll first talk to nmixter and if necessary will try fixing the polygons myself (first backing up the data with JOSM).

Thanks,

  • Alex
(22 Mar '13, 16:29) Alexander Av...

Yes, the rendering problems are caused by several areas which are overlapping with the lake.

Most of the lake is covered by this area, for Anderson Lake County Park: way 28461629. This is tagged as leisure=park - this area may be a "county park", but it seems it doesn't meet the OSM definition for leisure=park, ie "open, green area for recreation". It should probably be tagged with boundary=national_park or boundary=protected_area instead.

Also the lake is surrounded by a way which is an outer part of relation 1696825. This relation is tagged as landuse=meadow. The lake doesn't meet the OSM defintion of meadow "land primarily vegetated by grass plus other non-woody plants", so shouldn't be tagged as that. It appears that relation is from an import of government data for farmland.

It would be worth contacting the user who originally added this (nmixter), or discussing it on the talk-us mailing list, to agree how these areas should be mapped and tagged.

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answered 22 Mar '13, 13:24

Vclaw's gravatar image

Vclaw
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accept rate: 22%

I have just compared the mapping (in PotLatch2) of your lake with the mapping of Coyote Reservoir which is to the South East. The only difference is that Coyote Reservoir has a Multipolygon relation, with an ID and Role is set as Outer (Ditto this for Lake Windemere, Cumbria, UK) whereas Anderson Reservoir appears to have this Relation missing. Not sure if this is a solution or not.

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answered 21 Mar '13, 19:27

AliOnHols's gravatar image

AliOnHols
56112
accept rate: 0%

Hi the Anderson lake should be tagged as inner polygon inside the leisure park just to appear properly now it seems the be partly green park. The Coyote lake is partly a 2 (broken) multipolygon and should be tagged inner (natural water) and outer (park) in the advanced menu P2. What’s the use of the thin line (multipolygon with 95 others) following the waterline more or less ? Whats the main outer polygon ? Or just ask the editor nmixter why it has be done ? By sending the last editor a simple mail with your remarks. It might get you an answer as well ! And MK 408 as well for the southern lake. You can find or identify the editor by using the button H if the node or nodes are marked. In JOSM its on the right in the scrolling menus. Greetz

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answered 21 Mar '13, 20:26

Hendrikklaas's gravatar image

Hendrikklaas
8.5k178210351
accept rate: 6%

Should the outer polygon totally contain the inner one? which it doesn't in this case as we can see the white area on the map. If only half the lake is in the park should the lake be in two sections? good point about contacting mapper. Maybe part of blank polygon could be used take the park polygon around the edge on the lake??

(22 Mar '13, 12:22) andy mackey

alt textThere appears to be two polygons around the lake one tagged lake the other without any tags,which I think may be the problem. I would be reluctant to delete the blank one as it would been difficult to re-do. I use potlatch2 but I believe it is easier to retain the polygon on your PC to put back if necessary if you are using JOSM. Hopefully a more experienced mapper will know the safe procedure. here is the blank polygon.

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answered 22 Mar '13, 11:14

andy%20mackey's gravatar image

andy mackey
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accept rate: 4%

edited 22 Mar '13, 11:20

2

I certainly wouldn't delete the untagged way - you can see in that screenshot that it's part of a multipolygon relation!

(24 Mar '13, 09:05) Andy Allan
1

Additionally ways without tags and without being member of any relation are rarely a problem, if ever.

(24 Mar '13, 09:44) scai ♦
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question asked: 21 Mar '13, 17:45

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last updated: 24 Mar '13, 09:44

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