TIGER fixup

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The TIGER Edited Map ([1]) map shows which areas of data have been changed since the initial import

The Duplicate nodes map ([2]) is a good indication of areas which need more attention

Waychains analysis ([3]) identifies problems with interstates

The TIGER data are of variable quality. Here are some common problems that you'd find in unedited TIGER data:

• Wrong-way motorway
• Wrong-way motorway-link
• Missing bits of motorway or railway
• Only one way to represent a two-carriageway highway
• Wrong road classifications
• roads joined that shouldn't
• roads that cross on different levels get intersection nodes
• railway and roads moved so they intersect when they don't
• whole subdivisions misplaced by dozens of meters
• distorted subdivisions
• missing subdivisions
• many points used to position a road wrongly
• missing layer information
• using obscure never-used rather than common names
• missing ref on highways
• "braided" streets
• entire roads that no longer or never did exist
• some counties were imported twice. TIGER duplicate counties have now all been fixed

Each uploaded way has a tiger:reviewed=no tag. Once you have reviewed a way, you can delete this tag.

Contents 1 Road Alignment 2 Connectivity along county borders 3 "Over-Connectedness" 4 Divided roads 5 Braided streets 6 Useful tools 7 See also

Road Alignment

Probably the biggest problem with TIGER data is that they were originally created for taking census surveys, not for making maps. This means that in many areas the roads aren't aligned with their true position, but if you imagine the TIGER database as a sketch for people walking around with clipboards, then it has all the roads laid out roughly correctly. The work then needed is to drag everything into its correct place and add more nodes to smooth out curves. SeeTIGER fixup/Alignment for HOWTO information on re-aligning roads, and a list of counties with widespread problems.

Connectivity along county borders

There are particularly serious data problems along county lines, where different TIGER datasets were imported. County lines show up as administrative borders at zoom level 9 (e.g.). The main problem is that each county import didn't "know" about adjacent neighbours, so created duplicate nodes where the end of a road meets the start of its continuation (or "twin brother") from the next county. This even affects major highways so prevents most Routing between counties. Other problems include overlapping roads and border ways - for example, when a road runs along the border it will have been uploaded twice in exactly the same place - once from one county and once from the other.

There is a HOWTO available on fixing this problem.

"Over-Connectedness"

The original TIGER data has no concept of whether two roads are connected or not - so that was all synthesised during the import into OpenStreetMap. For grade-separated roads this causes problems when routing.

There is a HOWTO available on fixing this problem.

Divided roads

Many Interstates and other major roads only have one carriageway in TIGER - when in reality, they have two one-way carriageways ("divided road" or "dual carriageway").

There is a HOWTO available on fixing this problem.

Braided streets

Some streets in the TIGER upload were "braided", where the one-way highways of a dual carriageway criss-cross back and forth across each other, sometimes going in the wrong direction for the side of the street on which they run. The ones that were identified shortly after the upload were fixed using the osm-unbraid tools. The following counties are known to have remaining braided roads:

• Polk County, Florida (mostly clean now)

Please Note: "braided" refers only to the situation where the ways are indiscriminately on the wrong side of the street for their direction. It is a reasonable and well-used technique to bring the ways of dual carriageways back to a single point intersections to facilitate and simplify the mapping of control devices and turn restrictions. In other words, you may see situations that look similar to the picture, but are correct because the ways both stay on the correct side of the center divider between intersections. In all cases, like any other edits in OSM, be careful not to lose any existing correct data contributed by your fellow mappers.

Useful tools

You can jump from one slippy map to another, keeping the same position, with the mapJumper bookmarklet. Two ways :

• Just drag the mJLite bookmarklet on your tool/favorite/bookmark.

On a well formed url map (with lat, lon, zoom), by clicking on your mJLite bookmark, you will be led (in a new window) to the mapJumper hub page where are proposed survey links.

• Just compose your bookmarklet here, with the preset import or survey. Paste the code in a new bookmark. Name it, let's say, mJ[Tiger] (you can get other mapJumpers).

On a well formed url map (with lat, lon, zoom), by chosing the mJ[Tiger] bookmark, give the shortkey for the Tiger fixup service (tf). Validate and jump.

In Potlatch, you can choose to "Highlight unchanged TIGER data" (in the options dialogue). This will give a pink border to roads which have not been changed since the initial import.

Again in Potlatch, if you hover the pointer over a way where the tiger:reviewed tag is set to "aerial", the name will be followed by a *.

In JOSM, you can see that unreviewed TIGER data (that is, with tiger:reviewed=no) shows up with a yellow-ish background.

Other handy fixup plugins include the WayDownloaderPlugin

See also

• TIGER to OSM Attribute Map
• http://www.nabble.com/JOSM:searching-for-tags-with-colons--searching-for-multiple-keys--layers-t4363562.html