Why Google Earth Doesn't Line Up

B.F. explains why things like boundaries don't line up on Google Earth:

You complained that the Canada-US boundary does not follow the 49th parallel and is not a straight line in Google Earch. You are only partially correct. I agree Google Earth sometimes does not draw the border correctly (take a look at the Peace Arch at the Blaine crossing).

On the other hand, contrary to poular opinion, the long, straight portion of the Canada-US border is not quite straight and does not follow the 49th parallel. Yes, that was the intent and the wording of the original treaty.

However, two problems arose:

1. They assumed the world is round. It isn't; the diameter through the poles is a couple of hundred miles less than the diameter at the equator, and it is fatter south of the equator than north of it, sort of like a pear. Technically the earth is a "geoid", which means "earth-shaped".

2. Item 1 was compounded by surveying errors.

When the problem became apparent, both countries ageeed that the simplest solutuion was to re-define the border as being a series of straight lines that connected the existing 1,000 obelisk-shaped markers all along the border.

The "49th parallel" section of the border actually wanders north and south of the parallel by an average of 90 yards or so. For example, Monument 48 is located on the Columbia Valley Highway south of Cultus Lake. It is actually south of the 49th parallel at north 48 degrees 59 minutes 55.6 seconds.

I have 1950's vintage government topographical maps of this area that show it at 49-00-00, whereas the current version of the same map locates it correctly. Interestingly, the monuments furthest north of 49 are just south of Abbotsford Airport.

For further information, check out internationalboundarycommission.org and the Degree Confluence Project, which correctly places some 49th degree confluences north of the border and others south of it.

Comments

[zmarties]

I couldn't get the given URL to work - looks like

http://www.internationalboundarycommission.org/ibccoord-nad83.htm

is the nearest match.