Originally Posted by aterpster
I can't answer that other than to relate the errors in the continental U.S. before they made the conversion.
On the coasts it was as little as a couple of feet.
In Kansas it was as large as 1,000 feet, or so, in longitude, but much less in latitude.
I think that you may not remember this correctly. I was working as a geodetic surveyor during the era of the conversion and recall the differences being much less. To kind of refresh my memory, I looked up a geodetic control point in Kansas and compared the NAD27 coordinates with the current NAD83 (for charting and navigation purposes identical to WGS 84 coordinates) the difference between the two is about 47 meters for that particular reference point. I think that the largest differences you're going to find between the two are in Alaska where it was on the order of 120-130 meters. That's for the US though. In response to the question about Africa, there's no telling. Prior to the development of global Datums generally every country was on it's own, which nay or may not match the rest of the world.