[Talk-us] Proposed cleanup: NHD "rivers"

john at jfeldredge.com john at jfeldredge.com
Sun Mar 20 21:41:57 GMT 2011

Has anyone determined for sure that the streams you plan to tag as intermittent are so, in fact?  This would require either getting confirmation from the organization that made the original survey, or at least checking with folks with local knowledge that a large. enough sample of the streams were, in fact, all intermittent.

-------Original Email-------
Subject :[Talk-us] Proposed cleanup: NHD "rivers"
From  :mailto:penorman at mac.com
Date  :Sun Mar 20 16:29:54 America/Chicago 2011

A mapnik rendering change has revealed a problem in some areas with NHD
imported waterways. An example of the problem is at

Essentially, all the streams are tagged as waterway=river, with
waterway=stream being used for what appear to be intermittent streams.

I propose doing the following changes. These changes would *only* be done to
ways that have not been modified since import. I have experience with this
type change from cleanup on Canadian NHN data.
1. Adding intermittent=yes to NHD streams.
2. Downgrading waterway=river to waterway=stream for non-rivers. 
3. Joining rivers into a single way

Steps 1 and 2 would be done in one set of imports while joining rivers would
be done in a second pass. 

Spot checks in the area linked indicate this would cause no problems. If
verification with imagery was necessary I'd use MapQuest's Open Aerial Map
as it seems to be the highest quality in these remote areas. 

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John F. Eldredge -- john at jfeldredge.com
"Reserve your right to think, for even to think wrongly is better than not to think at all." -- Hypatia of Alexandria

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