1. The Four Corners monument marking the spot where borders of Arizona, New Mexico, Colorado, and Utah meet. Even after several lawsuits and court rulings, it's still off by half a kilometer or so.
(https://en.wikipedia.org/wiki/Four_Corners_Monument#Misplace...)
1. The Four Corners monument marking the spot where borders of Arizona, New Mexico, Colorado, and Utah meet. Even after several lawsuits and court rulings, it's still off by half a kilometer or so.
Reading the Wikipedia article, it appears that the monument is off from its originally intended position, but that it has been confirmed by the courts that the surveyed markers supersede the written descriptions and therefore define the border. In other words, it makes no sense to say that the four corners marker is misplaced as it is by definition where the corners meet.
Another interesting example of marks and boundaries in the physical world superseding surveys and agreements is the USA/Canada border west of the great lakes. While officially the 49th parallel, the border was manifested in the real world as a series of straight lines between hundreds of monuments. These were set down without GPS, and at times wound around obstacles, so there's a fair degree of variability in how close these monuments actually are to 49deg: http://www.confluence.org/country.php?id=3#NOTES
The zigzag is actually fairly easy to see on Google maps, because the border is maintained by both the US and Canada, clear cutting the lines in forested areas. This highly visible physical boundary is the true national border.
Ecuador has a city/monument running through the "Middle of the World", (the equator line as calculated by French Academy of Sciences in 1736).
As it happens, however the equator actually lies about 240 meters north of the marked line.
Having been there, its funny to see how many tourists take photos straddling the 'equator', evidently the expense of relocating the monument to the actual equator isn't viable.
This is pretty funny, especially since they had an opportunity to fix the mistake after advent of GPS. Thanks for this!
As an off-topic, I actually visited Quito, but didn't know about the monument. I did, however, cross the equator on the New Year's Eve while en route between Galapagos islands. I still have the screenshot of my Android screen showing the 0º 0' 0" latitude close to midnight. A lot of my work at the time had to do with navigation and positioning; I got a kick out of the Galapagos airport code for that reason.
> 2. Prime Meridian mark (that goes through the Royal Observatory in Greenwich) is off by 102.5 m
No it ain't, it's right on the meridian by definition. Some other co-ordinate system's 0° meridian is adjacent & almost coincides, but for a 102.5m offset.
What definition do you refer to? The real explanation for the discrepancy is that due to local gravity effects, the local vertical at the observatory does not intersect the Earth's rotation axis.
When the Airy transit circle was built, a mercury basin was used to align the telescope to the perpendicular. Thus the circle was aligned with the local vertical or plumb line, which is deflected slightly from the normal, or line perpendicular, to the reference ellipsoid used to define geodetic latitude and longitude in the International Terrestrial Reference Frame (which is nearly the same as the WGS-84 system used by GPS). While the local vertical defined at the Airy transit circle still points to the modern celestial meridian (the intersection of the prime meridian plane with the celestial sphere), it does not pass through the Earth's rotation axis. As a result of this, the ITRF zero meridian, defined by a plane passing through the Earth's rotation axis, is 102 metres to the east of the prime meridian. A 2015 analysis by Malys et al. shows the offset between the Airy transit circle and the ITRF/WGS 84 meridians can be explained by this deflection of the vertical alone; other possible sources of the offset that have been proposed in the past are smaller than the current uncertainty in the deflection of the vertical near the observatory.
So with WGS-84 and the ITRF, we changed to a different coordinate system with a meridian that goes 102.5m east of the Greenwich observatory. This was done to keep continuity in UT1 time.[0]
The one that goes through the marker. If there's any ambiguity due to another meridian having the same name, I trust you can distinguish them with your common good sense.
When a tree falls in the forest, does it make a sound? What a silly question: It's just semantics! Of course, it does release acoustic energy, when its motion causes vibrations in the air. If there is no one near enough for this energy to move their eardrum and be perceived by the brain, no one will hear the tree fall.
Likewise, are these landmarks in the right location? George is saying that the 4 Corners monument and the Greenwich meridian were supposed to be at certain points, and they were installed at different points. You're retroactively redefining those points to be "where the monuments are".
It's perfectly reasonable to talk about the difference between the intended position and the actual position, and when the intended position makes more sense - for example, going X degrees east or west of the meridian should put you at X degrees. If the meridian does not go through the axis of rotation of the earth, so that measurements at other points do not put you at X degrees, it's sensible to say that the meridian is off.
Such carelessness was fairly normal for the time: the surveyors were often under pressure to complete quickly, even in the worst territory, with poor equipment and little actual training. On top of that, they were often bribed to move boundaries one way or the other, or interested themselves in engaging in land speculation, so were less than honest in their surveys.
Anyone interested in this fascinating history should read Andro Linklater's Measuring America.
Tennessee and Georgia have been in a somewhat long-running dispute over a surveying error with their shared border. Georgia seems to be particularly interested in the water in the Tennessee River, which would flow through GA if the border were moved. This has led to some humorous moments, e.g. "[i]n 2008, former Chattanooga Mayor Ron Littlefield sent an aide, who reportedly wore a coonskin cap, and a city councilman to Atlanta with a truckload of bottled water during a previous chapter of the dispute."[0]
I was initially very impressed at Tennessee's resolve in protecting the water. Just a few miles later, the river flows into Alabama, where I initially thought that Tennessee would cease to care about what happens downstream. But then I looked further and realized it flows back North through central Tennessee.
What's stopping Alabama from selling the water to Georgia?
1. The Four Corners monument marking the spot where borders of Arizona, New Mexico, Colorado, and Utah meet. Even after several lawsuits and court rulings, it's still off by half a kilometer or so. (https://en.wikipedia.org/wiki/Four_Corners_Monument#Misplace...)
2. Prime Meridian mark (that goes through the Royal Observatory in Greenwich) is off by 102.5 m. (https://productforums.google.com/forum/#!topic/gec-nature-sc...)