[Talk-ca] GeoBase and OpenStreetMap

[Dave Hansen]

On Wed, 2008-12-17 at 00:26 -0800, Dan Putler wrote:
> One way has the TIGER TLID attribute, the other way does not (the person
> doing the editing of the way missing the TLID probably didn't understand
> the relevance of it, and didn't think it mattered).

There are several concerns here.  First, as you pointed out, is that we
have virtually no control over what other users in OSM do.  There are no
access controls or integrity constraints beyond some very simple ones.
If we decided to strongly preserve the tiger TLIDs (or their GeoBase
equivalent), I'm not even sure it would be possible without some serious
changes to how OSM works.

> Moreover, in looking
> through the data in this area, I determined that a _large_ number of
> ways cover multiple block faces (so can't have a single TLID).

Yes, virtually all TIGER objects represented as a single TLID were
merged into larger ways in the OSM import.  

> In these
> cases, the only way I can see to attach the TLIDs back on to them is to
> import them into GRASS, clean and break the ways at intersections, and
> then attempt to match them back to the original TIGER data using a
> combination of street name, proximity, and bearing. It can likely be
> done to an acceptable level of precision, but what a pain! If you have
> the tools to deal with these issues already, and do so on a regular
> basis, my concerns are misplaced. If not, then they are legitimate
> concerns.

Oh, I don't have the tools to do it.  I haven't had the need to write
them.

If you really want to track the GeoBase ways after they are imported,
what about looking at the planet diffs?  You could keep a record of what
happened to each object as it gets modified by users.  There would be no
need to match up data because you would know how each piece got there.

-- Dave