Thursday, November 10, 2005

Geodetic Survey

Do you recognize the artifact at right?

It’s a U.S. Coast & Geodetic Survey marker; this particular one on the peak of Cuyamaca Mountain in the San Diego County mountains. It’s a simple bronze disc, three inches (7.5 cm) in diameter, embedded in some permanent and hopefully immovable object. In this case it is embedded in a large rock formation at the summit of Cuyamaca.

There are over one million of these markers in the United States. The vast majority of them were placed long before modern technologies like GPS and laser rangefinders made surveying relatively cheap and easy. The surveyors who placed most of these markers used old-fashioned optical/mechanical surveying instruments, and processes that depended heavily on repetition and cross-checking for accuracy. And these processes were, by today’s standards, almost unbelievably manual. The surveyors walked, hiked, or rode horses to their remote destinations. For the most part, they carried their instruments on their backs. They recorded their observations in log books, in pen-and-ink. And perhaps most amazingly of all, they did all the calculations manually — they couldn’t even use a slide rule, as the precisions they were working with were far higher than were achievable with a slide rule.

The official U.S. Coast and Geodetic Survey started in 1807, and continues to this day (though in a new agency). Thousands of surveyors working for almost 200 years — and these little bronze discs (and the data that records where they are) are perhaps their most important work product.

The little discs are important because they are the starting point of virtually every other survey, whether by government or by private industry. They are the starting point because their absolute position is known more accurately than any other collection of points. Every real estate survey is referenced to one or more of these markers. American cartography is universally traceable back to these markers. Political boundaries (states, counties, cities, etc.) are all traceable to these markers. Pretty important job for a humble little piece of bronze!

Because our hiking (over the past forty plus years) has taken us to many peaks and prominences, we’ve run into many of these markers. Long ago I fell into the habit of searching for them each time I reached a likely looking spot — and more often than not, I’d find one. Sometimes I’d have to brush off dirt and leaves to find it, so I’d know it’s been some number of years since anyone had “visited” that particular marker. On a few occasions, I’ve run into bright, shiny, brandy-new markers — very unexpected, as most of them date back 20 years or more. The oldest one I’ve every spotted was on a peak near Mt. Katahdin in Maine, called “South Brother"; the marker there was dated 1876.

If the story of the American geodetic survey intrigues you, you can find some more information (and pictures) here, here, here, and here.

Cuyamaca Autumn

These are some more photos from the hike that Debi and I made up Cuyamaca Peak this past Sunday. As usual, clicking on any of the will bring up a larger view.

The images in the top row all show some aspect of the destruction wrought by the fire. The two outer ones are obviously charred logs; the center one is a dead oak, it’s bark burned by the fire so badly that it sloughed off. What you’re seeing is the wood immediately under the bark, with the characteristic oak texture (lots of pores) clearly visible, along with the trails of some insect that ate its way along trails just under the bark. Presumably the bugs were well toasted in the fire!

The second row are the autumn flowers, of which there are a dozen or so species in bloom presently. They made beautiful splashes of color, contrasted against the somber autumn tones and the stark blacks and grays left by the fire. I don’t know what any of these flowers are.

The bottom row is the kind of thing folks in other climates see very commonly: the “fall color” of the leaves of deciduous trees. We have it here in southern California as well, but not with anything remotely resembling the wild abundance of color that is the norm in places like New England or the Appalachians. But we cherish what we have…

Everest on Mars

Spirit and Opportunity — the extraordinarily successful mobile probes on Mars — have now been operating for very close to two years. Not bad at all for missions designed to last just three months!

Recently Spirit climbed to the top of the Columbia Hills, and on a peak the scientists at JPL have named “Everest", the Spirit probe paused to take this 360 degree panorama of the spectacular view it was enjoying. You can click on the image at right to get a slighly larger view — or you can go to the rover site to get a truly enormous (40+ MB!) version, nearly big enough to wallpaper your livingroom with.

I’ve repeated this so many times I’m sure my long-timer readers are bored to hear it again, but … these two probes are making manned space exploration (at least as it’s currently practiced) look like a positively silly waste of time, energy, and money. And they’re not alone — Spirit and Opportunity have dozens of “brothers” and “sisters", like Cassini-Huygens around Saturn, the Hayabusa probe, and many more. Many of those probes all by themselves are producing more good, hard, useful science results than all of the manned space missions combined. And they’re doing it for one helluva lot less moolah…