Monuments of Misdirection

[Image: Monumentalizing mismeasurement in Ecuador; photoby Meridith Kohut for the New York Times, courtesy of the New York Times].

At the end of her forthcoming book The Measure of Manhattan, author Marguerite Holloway refers to the impossibility of precisely locating, using today's GPS technology, the bolt left behind by surveyor John Randel, her book's subject, back in 1811 as he staked out Manhattan's future grid.

Being on the road right now, I don't have my copy of Holloway's book with me, so I won't be able to quote her book directly; instead, I will rely on the New York Times for some brief context. Randel spent "10 years staking out and marking the intersections from First Street to 155th Street with 1,549 three-foot-high marble monuments and, when the ground was too rocky, with 98 iron bolts secured by lead. (He had to resurvey 30 miles after vandals or disgruntled property owners removed the markers.)"

Manhattan at that time was thus, however briefly, a kind of game board or field of acupuncture points—a ghost grid, in advance of the city it surveyed—with thousands of monuments and bolts pinning down the spots where streets and intersections would soon appear.

Holloway's concluding point, however, is that even something as real and tangible as Randel's iron bolts, anchored by lead into solid bedrock, nonetheless remain extraordinarily difficult, if not impossible, to map with objective accuracy. The earth slips outside of our satellites and survey systems, even if only by a fraction of a centimeter, always just beyond the promise of perfect measuring.

[Image: The grid arrives before the streets it surveys].

I thought of this recently when two quick stories popped up on my radar:

1) Down in Ecuador, a country named after the Equator that passes through it, a monument dividing the northern and southern hemispheres is, as it happens, in the wrong place:
Those who visit the Middle of the World, a government-owned park that pays tribute to the Equator, are not drawn by the trinket shops or cafes offering roasted guinea pig. They want to stand on a yellow line painted on the ground here that is said to be precisely at Earth’s midpoint—0 degrees latitude, 0 minutes, 0 seconds.

Except that it is not.

The Equator is hundreds of feet to the north.
According to one person there, the ground conditions at the actual Equator are not stable enough to hold a monument nor to welcome the huge crowds that regularly arrive to see it; according to someone else, however, the monument's original builders "believed they were placing the monument in the correct spot, except that measuring techniques at the time were not as accurate as they are today, so they were off by a few hundred feet."

This is why a private counter-monument has been built, supposedly on the real Equator, in a place called Inti-ñan: "just a two-minute drive from the Middle of the World, at a small, privately owned site called Inti-ñan, there is a sign on a gate saying that its location is 'calculated with GPS' to be exactly at 0 latitude." However, as we glimpsed with the help of Marguerite Holloway, commercially available GPS is not as precise as most people believe it to be, and it is subject to its own asynchronies and drifts. (For those of you interested in the political implications of inaccurate mapping technologies, amongst other things, be sure to keep a look out for Laura Kurgan's Close Up at a Distance: Mapping, Technology, and Politics this coming spring).

[Image: From Laura Kurgan's You Are Here: Information Drift, 1994].

As such, we read, even nominally accurate GPS readings at Inti-ñan actually "varied depending on how devices were calibrated. That, [a local guide] said, was why, on this occasion, a visitor's GPS held over the line of bricks that Inti-ñan uses to mark its claim to equatorial exactitude showed that it was still several yards to the south of where it ought to be."

Passing their GPS receivers over the monument like dowsing rods or geodetic ghost detectors, these tourists of the world-system would thus realize, again and again, that they both were and were not standing in the wrong place, both arriving at and never quite reaching their destination.

2) The south pole is also adrift, surrounded by rings of obsolete monuments. Indeed, "in Antarctica, 'X' never really marks the spot."

In a recent piece for the Guardian, Frances Stonor Saunders explains that "the south pole doesn't stay still."
It drifts at a rate of about 10 metres a year, and because of the Earth's axial tilt... it also wobbles. Every New Year's Day, the pole's marker is moved to indicate its new position, though in the time it takes to drive the marker into the ice-pack the pole has already shifted slightly.
In fact, Saunders points out, "There are other poles on Antarctica, and they too move around, pursued by scientists with their markers."
There's the pole of inaccessibility, for the greatest distance from a coast; the cold pole, for the most frigid place; the pole of variability, for the spot with the greatest range in atmospheric pressure. The most (upwardly) mobile is the south magnetic pole, which has moved over 500 miles north-west since its discovery by members of Shackleton's Nimrod expedition more than a century ago.
All these lines and tropics, equators and poles, passing back and forth over the fallible monuments that mark them, as entire planet-spanning systems of measurement and location miss their marks by inches, feet, kilometers, degrees, momentarily accurate but almost always wrong.

(Antarctica story spotted via @nicolatwilley).

Comments are moderated for spam only.






3 Comments:

Anonymous Anonymous said...

The brass line at Greenwich where tourists get themselves photographed straddling the East and West is also several degrees out. The much less pretty line in white paint that goes across the road is in the right place, but nobody queues up to be photographed next to it.

December 18, 2012 3:42 PM  
Blogger Kaleberg said...

There is a big difference between consumer GPS units designed for navigation and professional units designed for surveying. The consumer units make all sorts of assumptions about how they are being used and how they may be moving at typical consumer speeds. The professional units simply perform a complex integration and error minimization assuming a static placement. I remember using a unit in the early 90s and simply setting it up and letting it collect data for a couple of days. The error bars got real small. (I was sort of a spectator to this. The project was being run by some geodesics guys.)

The real problem comes from the fact that the earth's surface is in motion as can be measured with a pair of good GPS units. This is amplified by variations in the earth's rotation as it "rings" in response to seismic events, something that can also be measured using GPS units. One might perfectly measure the equator or some meridian and still leave future generations baffled or bemused.

December 23, 2012 11:09 PM  
Anonymous Tijmen Stam/IIVQ said...

What surprizes me most is that old surveyors were able to start digging mile-long tunnels from two ends and still lined them out to within feet, sometimes inches of each other!

March 10, 2013 4:14 AM  

Post a Comment