[Talk-us] Remapping coastlines

Toby Murray toby.murray at gmail.com
Sun Mar 25 07:10:44 BST 2012

So I got some NHD shapefiles from Phil. Unfortunately coastlines are
hard. The nodes tend to get incorporated into all kinds of other
things like beaches, piers, etc so I can't just do an xapi query and
replace things wholesale like I did with the state boundaries.

So far I have only done a few miles of coastline from the Mexico
border to north of San Diego. The good news is that there are a lot of
the ways have been *heavily* modified by an accepting user since the
original import. So for example in a way with 100 nodes, there were
sometimes 4 or 5 dirty nodes. I just removed these nodes and then
marked the way with the odbl=clean tag since all the original geometry
had been replaced and the tagging is trivial.

In a few sections where most of the nodes were still dirty I did end
up importing the NHD stuff in small bits. I'm not sure how the rest of
California will look. I'm guessing there will be large sections that
will need wholesale replacing. I think there will also be more areas
similar to San Diego with heavy modifications by accepters.

But it is slow going so please feel free to jump in. I am done for now
and probably won't do much more until tomorrow afternoon. So far I got
up to about here:


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