TIGER fixup/250 cities/duplicate nodes

Looking at duplicate nodes provides an alternative way of seeing which areas need most fixing. Remember fixing duplicate nodes is not the only problem to work on though. We'd like basic routability, but let's do a proper job of fixing up all the problems as we work our way along the interstates.

A lot of these problems are caused by the county borders in TIGER and there's a howto to help you get started fixing them. Other duplicate nodes may occur accidentally in the editing process, as it may be difficult to tell whether the cursor is in a position where it will join to existing ways or create a new node. Finally, users who are used to a non-topological model of data (e.g: as used in most conventional GIS products) may assume that the nodes join automatically - unfortunately they don't.

Maps

These old "250 cities" maps have been superseded by Duplicate nodes map

The duplicate motorway nodes map is all clear! It used to show duplicated nodes on any highway=motorway. Proceed to level 2...

The duplicate 'important' highways nodes map shows these errors on ways tagged as highway=primary, highway=trunk and highway=motorway. Be careful - this link needs a browser with a recent javascript engine to handle the number of markers. We suggest a recent version of Firefox, Safari or Google Chrome.

The duplicate highway nodes map shows these errors on ways tagged with road types as a tile layer. The road types used are: motorway, trunk, primary, secondary, tertiary, residential, unclassified, service and road, plus associated _link types.

Progress

Here's the history showing the number of dupe nodes decreasing as the data gets fixed.

Firstly dupe nodes on highway=motorways:

...and for dupe nodes on other 'important' highways: