[Imports] Vermont Town boundaries from VCGI

Apollinaris Schöll aschoell at gmail.com
Wed Aug 8 19:10:57 BST 2012


On Wed, Aug 8, 2012 at 6:49 AM, Andrew Guertin <andrew.guertin at uvm.edu>wrote:

>
>
> The state boundary in the VCGI file (which exactly matches the outer
> boundary of the towns in the VCGI file) does *not* exactly match the
> state boundary in OSM.
>
> In most cases involving straight lines it is reasonably close--within
> about 10 meters. In a few areas of the middle-of-the-lake border with
> New York, they diverge by over 100 meters. In on the river border with
> New Hampshire (the border is specifically the low water mark of the west
> bank of the river), there are some places where the river has shifted
> (e.g. to cut off an oxbow) and this is reflected in one version but not
> the other. There are also some places where the the two versions match
> but do not match the bing satellite imagery. Interestingly, on the
> US-Canada border, most of the nodes seem to be exactly the same--OSM has
> them marked with survey point reference numbers, so this would make
> sense--but shifted a few centimeters. Probably something to do with
> projections.
>
> I plan to keep the existing state and national borders, and manually
> connect the new town boundaries with the existing state border.
>
>
state boundaries might be wrong. In case you can verify your data is more
accurate then feel free to change it. Especially boundaries imported from
Tiger are often wrong.

and a comment to your initial email. downloading borders with XAPI seems a
good idea but you will get in big trouble when you try to delete and upload
to the server. In all places where a node is shared with other ways it will
create a conflict and you will spend hours to resolve them.
I have used a different approach in the past. Do all the work with the new
boundaries in JOSM but don't delete the old boundaries. Then work online
with Potlatch to delete the old boundaries. Potlatch will load only the
ways in current view and can delete a whole long way without creating a
conflict.
The other option is to make sure all nodes of the boundary are loaded
together with all ways using them. I think osmosis has some functionality
and maybe the Overpass server can do it also.
And a final hint. Start to work on some smaller ones first and keep the
uploads small enough. Conflict resolution can turn into a nightmare.
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