[Talk-us] City boundaries on the Canada/US border

Paul Norman penorman at mac.com
Fri Mar 30 10:17:42 BST 2012

There are a significant number of cities in BC and Washington which have
borders that in practice[1] coincide with the Canada/US border. Currently in
OSM these are represented with many nearly-overlapping ways.

The Canada/US border here consists of the BC-WA border, BC-ID border, BC-MT
border, AB-MT border, SK-MT border, SK-ND border, etc. There are separate
ways for the cities on the Canada side and cities on the US side.

I am considering replacing these with one set of non-overlapping border
ways. This would involve splitting the ways whenever a city ends or begins
on either side of the border. The border would then consist of a BC-WA
border in the water, a Surrey-Whatcom County border (in the water), a White
Rock-Whatcom County border, a Surrey-Whatcom county border, Surrey-Blaine
border, Langley-Blaine border, Langley-Whatcom County border,
Abbotsford-Whatcom County border, Abbotsford-Sumas border, etc.

This would reduce the number of ways present when you download a section of
the border and have many advantages. The one big disadvantage is that it
would boost the number of ways in the Canada and US relations. This
increases the chance of conflicts and also increases the number of places it
could be broken.

Either way, the Canada/US border will remain very complex with so many
different boundary relations ending there.

If I do this, I will also align the borders to the IBC data (PD). I've
investigated the accuracy of their data, and it agrees with the markers on
the ground to within 10cm. I believe the most significant source of error in
their data is the NAD83 to WGS84 conversion.

[1]: The actual legal situation is much more complicated and serves as a
good example of the problems that arise when you define what is supposed to
be one line in multiple ways. The biggest oddity is that the Washington
border extends out of the United States into Canada. All of the other
oddities are just a few meters at most.

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