[OSM-newbies] Fixing the Mississippi River

David Groom reviews at pacific-rim.net
Fri Sep 2 10:45:34 BST 2011

> ----- Original Message ----- 
> From: "Dan Ball" <danpelota at gmail.com>
> To: <newbies at openstreetmap.org>
> Sent: Monday, August 29, 2011 7:35 PM
> Subject: [OSM-newbies] Fixing the Mississippi River
> Hi all,
> I've been tinkering OSM data for the first time over the last week and


welcome to OSM.

> finding my way around. I've stumbled upon something interesting: the
> riverbank of the Mississippi River seems to be missing between Maxey 
> Island,
> IL 
> (http://www.openstreetmap.org/?lat=39.0043&lon=-90.6892&zoom=13&layers=M)
> and just south of Quincy, IL
> (http://www.openstreetmap.org/?lat=39.897&lon=-91.4429&zoom=12&layers=M). 
> It
> seems the missing riverbanks cause the river to "disappear" between these
> two areas on the openstreetmap.org viewer.
> I'd be happy to contribute if the data are indeed lacking here – I've just
> never edited OSM data and wanted to clarify a few things before I started
> messing with such a major geographic feature:
> 1) The source of the riverbank data appears to be NHD where the features 
> end
> on both sides. Should these features be connected by hand, or should this
> hydrography data be imported from elsewhere?

I'd guess that in this instance its easier and quicker to trace these from 
the available aerial imagery

> 2) Does it matter whether the nodes are placed in a clockwise or
> counterclockwise matter?

Not really, though convention always was that outer ways got drawn 
clockwise, and inner ways anti-clockwise, but this became unnecessary when 
multpolygons started to be used
> 3) Should the addition be one multipolygon, or broken up into multiple
> multipolygons?

Definitely break this up into smaller sections. Its difficult to give any 
hard and fast rules on how many small sections to break this into, but if 
you have a look at the existing sections to the north and south of the 
missing section, I'd say they look OK.


> Thanks!
> Dan

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