[Talk-ca] GeoBase and OpenStreetMap

[Dave Hansen]

On Mon, 2008-12-15 at 14:55 -0800, Dan Putler wrote:
> There is one important difference between the Canada NRN and the US
> TIGER data. Specifically, the locational accuracy for the NRN is much
> better than is the case with TIGER. As a result, the need to undertake a
> big effort editing ways to fix their locational accuracy isn't going to
> be nearly as critical (put another way, what do you trust more,
> someone's Garmin eTrex or the provincial highway department's Trimble
> differential gps unit?).

>From the OpenStreetmap perspective, I think of it this way: do you want
to trust some government dude who drove down my street once and decided
how it should look on a map?  Or, do you want to trust *me* who is on
the street every day to decide how it should look on a map?

> As a result, the potential loss of information
> from "forking" the data is relatively more important for the Canada NRN
> then the US TIGER data.

I'm not sure I understand your argument.  Are you saying that coming up
with a plan to merge the OSM changes back into the NRN data is more
important that it would be for the TIGER?

> In my opinion the current US situation is
> unfortunate. As a data user you have the choice of one publicly
> available road network that is very good with respect to locational
> accuracy (OSM), and another that has much poorer locational accuracy but
> has address range and local area identifier information (TIGER) which
> allows it to be used in geocoding and certain types of routing
> applications (although, its locational accuracy is a problem for this).

I actually think that locational accuracy is one of the smaller problems
here.  Yes, some of the TIGER data are atrocious.  But, on a day-to-day
basis, I'd be willing to be that the consumer's GPS and things like
urban canyons cause more problems than TIGER inaccuracy. 

Are you saying that every single piece of data in the "GeoBase" data set
has been verified with "the provincial highway department's Trimble
differential gps unit"?  I'd certainly believe that a good bit of it is.
*But* a good bit of the TIGER data came from the same place: some very
precise state and local government surveys.  I believe the stuff created
from aerial (not even satellite) maps tends to be the worst for
locational accuracy.

> If the TIGER TILD's had been maintained on the OSM ways life would be a
> lot easier for a lot of potential users of the OSM data.

The TLIDs were preserved for each and every way.  I've introduced
changes into JOSM to even preserve them as data are modified.  Why would
you think otherwise?

-- Dave