[OSM-dev] TIGER import.rb

Andy Robinson Andy_J_Robinson at blueyonder.co.uk
Tue Jun 19 10:07:29 BST 2007


Dave Hansen wrote:
>Sent: 19 June 2007 1:06 AM
>To: Brandon Martin-Anderson
>Cc: dev at openstreetmap.org; Alex Mauer
>Subject: Re: [OSM-dev] TIGER import.rb
>
>I've noticed a few weird looking ways, like that the nodes aren't being
>connected in the right order.  I've traced it down enough to see that by
>the time the data gets to Dataset::to_osm(), it is already bogus.  So, I
>think if there's an error, it's in the TIGER parsing code.
>
>Although, I guess it could just be faulty TIGER data to begin with.
>
>Check out this .osm file:
>
>	http://sr71.net/~dave/foo/TGR18115.osm.xml.gz
>

I took a look over this file in a little more detail and have a couple of
observations which I hope are constructive:

1. A power line that runs through the area on a line SSW to NNE appears to
have short spurs that I guess are the local distributor from the main power
line. These and the actual power line itself currently connect themselves to
nodes on the highway network. Perhaps this is because in the TIGER data they
share the same node co-ords. I'd suggest that the reuse of nodes be limited
to each separate TIGER data type and not across data types. Would this throw
up any other issues?

2. The aggregation of segments into ways results in some instances in some
strange way patterns. Is this perhaps because there is insufficient
information in the TIGER data to differentiate where one logical way ends
and the next starts? Perhaps it might be worth seeing if splitting a way
where it makes a major change in direction (say greater than 60 degrees)
improves things. This should be applied only where the change in direction
occurs at a junction with another way.

Cheers

Andy







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