OpenStreetMap

admin boundaries: TIGER vs OSM...

Posted by rayKiddy on 27 August 2015 in English (English)

Wow. There are some interesting challenges in trying to figure this out.

I have figured some things out about how to find TIGER info in OSM. I can do things like look for “tiger:reviewed”=”no”.

I have downloaded a bunch of the TIGER data. I am going from the directories under ftp://ftp2.census.gov/geo/tiger/TIGER2015/. One challenge I am having is finding the longitude and latitude data. I know it is there somewhere. Is it in the files under EGDES? No. Under ROADS or ADDR? No. Only 40 or so more to check…. But I am looking at only the dbf files in those zipped files, using the dbf2mysql utility for Ubuntu. Is the lat/long data only in SHP files? That would be obnoxious.

But the TIGER data does have TLID fields. So this should help me. Because OSM features have a “tiger:tlid”=num value. So, I should be able to pick a TLID from the TIGER data and see it in OSM, or see and id on OSM and find it in the TIGER data, right? Maybe not so much.

I have over 12,000,000 edges. I have all of OSM. Can I find one place where an id appears in both? No. How should I search? Randomly? I have done a bunch of random checks and so far I hit nothing. Which kinds of id values appear in both? Does OSM only include polygon objects? Or any of the other 20 or so types in TIGER? There are so many ways to slice this. I am sure when I figure this out, it will be sooooooo obvious….. :-)

We will see.

Comment from TomH on 28 August 2015 at 07:29

I have no idea if this is the issue or not, but you do realise that the data in OSM is TIGER2005 and not TIGER2015 right? So it’s entirely possible the IDs just aren’t aligned between those two data sets…

Comment from joost schouppe on 28 August 2015 at 20:48

Yes, governments like their shapefiles. One “shapefile” is composed at least of a shp, shx and dbf file. The dbf contains the attributes (things like names etc.), the shp file contains the actual geometry. Free software like QGIS and expensive software like ArcGIS combine these into pretty maps. If you load the files into QGIS, it will probably make it easier to find what data has a copy in OSM.

I would expect admin areas to be relations forming a polygon (a closed line) in OSM. However, this random place has a closed line for a border: http://www.openstreetmap.org/way/33104058 (Relations allow several admin areas to contain the same lines as building parts. That means less data and easier editing: if you correct the border, all admin areas using that border are fixed) Maybe one of the several tiger:… contains an ID field you can use. The OSM id is pretty random, that you can basically ignore.

Comment from rayKiddy on 1 September 2015 at 04:07

Ok. Makes sense. I guess loading all of those dbf files into mysql was probably not a good use of my time. :-) O well.

thanx.

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