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Are these/many islands (Sandymush Creek river, N. Carolina) real/correct? The same with the river thickness? (Perma)link:
Please don't be too quick in down-voting/closing the question. The answer could explain a cause of a systematic error-class (huge number of cases). Thanks!

asked 02 Sep '13, 09:11

sanser's gravatar image

accept rate: 5%

edited 02 Sep '13, 10:57

scai's gravatar image

scai ♦

The same river has been "mapped" twice here: once as a centreline only (the thin blue line), once as a polygon (shape) with varying thickness. This gives the illusion of long islands between the two.

I say "mapped" in quotes because both are automated imports from NHD (the National Hydrography Dataset). Sadly, in this case, the importer does not appear to have adequately verified that they weren't creating misleading data before adding it.

If this is a one-off case then the best course of action is simply to fix this data yourself - probably by moving the centreline to the middle of the polygon (or, if the river is navigable, to the centre of the 'fairway' where boats would typically navigate). If it is endemic, however, you should raise it with the local mailing list (in this case, talk-us@) and someone skilled may be able to devise a semi-automated solution to fix it all in one go.

permanent link

answered 02 Sep '13, 09:54

Richard's gravatar image

Richard ♦
accept rate: 18%

edited 02 Sep '13, 13:12


From wiki waterway=river

"For wide rivers use Tag:waterway=riverbank to create separate ways for the two river banks. Note that a central way is still needed." - so really the centreline and the riverbanks should coincide, with the centreline being in the middle of the riverbank polygons. So it might be the centreline needs adjusting rather than deleting.

(02 Sep '13, 11:14) EdLoach ♦

Good point - edited accordingly.

(02 Sep '13, 11:23) Richard ♦

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question asked: 02 Sep '13, 09:11

question was seen: 3,306 times

last updated: 02 Sep '13, 13:12

NOTICE: is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum