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#1 2012-02-16 01:32:54

stephankn
Moderator
Registered: 2010-05-04
Posts: 606

Remapping critical infrastructure

Hi,

We still have a lot of remapping to be done during the next six weeks.

I would like to have the least possible impact on the data after April.

So this is my workflow:

I consider the loss of a motorway probably with full tags more severe than a residential road from aerial images without further tags.
I just completed remapping motorways and trunks in greater Bangkok using the procedure outlined below.

To focus on for example motorways and trunks I did a selective download in josm using Overpass:
http://www.overpass-api.de/api/xapi?way[bbox=96.78,11.82,104.8,16.35][highway=motorway|trunk|motorway_link|trunk_link][@meta]

This downloads all motorway and trunks together with their links.

Next I use the license check plugin to highlight problematic nodes and ways.

Then I zoom into these positions and do a regular OSM download. I fix the problem, usually the way was created by declining user amai with later tags added by agreeing users. So I had to replace dirty nodes using Bing imagery and GPS tracks. The tags that came from agreeing users are then reapplied to the new way.

With the same principle you could also work on other areas or select different elements for example waterway=river or railways, or ...

Stephan

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#3 2012-02-23 12:07:31

keng
Member
Registered: 2012-02-17
Posts: 10

Re: Remapping critical infrastructure

Hi Stephan,

Just to confirm that deleting those tainted nodes and draw the new one should solve this problem, am I correct?

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#4 2012-02-23 14:13:50

stephankn
Moderator
Registered: 2010-05-04
Posts: 606

Re: Remapping critical infrastructure

Hi Keng,

for nodes and ways it is easy. completely replace them with clean data. That could be either your own survey or other valid sources.

As most tainted ways are these that come from bing (or older yahoo) imagery it is fine to delete them and repaint from aerial images.

If there are tags on the ways like street names you have to check whether the user who entered the data has agreed. if yo you can take over this information.

This wiki page tells more details about remapping:
http://wiki.openstreetmap.org/wiki/Remapping


For relations it is a different thing. You first have to be sure that all relation members are clean. Then the relation itself needs to be replaced.

In JOSM the license change plugin helps a lot to detect which data is clean.

Stephan

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