Monday, March 12, 2012

Need true north? You might find it at your county seat.

In front of the old Hunterdon County Courthouse in Flemington, two curious granite obelisks stand, with thick oxidized metallic disks atop them. They're about 100 feet apart, and the one closer to the street corner bears a shield with the words "True Meridian 1883."

Ivan and I came upon these curious markers last month. They bear no explanation, no historical markers, and until we found the shield, we thought they might be fancy hitching posts for wagons. On further examination, and noticing the arrow etched on the top of one of the metallic discs, we knew these were utilitarian objects of a different sort.

Put together the location (the county seat) and the geographic term (meridian), and you could surmise that the obelisks have something to do with surveying, measurement or standards setting. You'd be absolutely right. After I got home, I did a little research and luckily found the story of how and why these markers came to be.

Before the days of global positioning satellites, surveyors counted on a number of mechanical instruments to find true north, and, by extension, property boundaries and mapped points. Trouble was, true north by their instruments wasn't always true north. Compasses can be compromised by other magnetic points in the Earth, and they're not all calibrated properly. Thus, measurements could vary from surveyor to surveyor, and they could even change from year to year. Coming to a commonly agreed-upon perpetual calibration standard for true north would go a long way toward clearing any confusion among land owners.

Inconsistencies like these were apparently frequent and troubling enough for the New Jersey State Legislature to act on a solution. In 1863 they deemed that a pair of true meridian markers be set at each county courthouse in the state, providing an easily-found tool for surveyors to regularly check the accuracy of their compasses. By law, every surveyor was required to set up his equipment on the meridian obelisk and record the magnetic declination readings at the county courthouse. (For those of us who didn't major in geography, magnetic declination is the difference between true north ("top" of the earth's axis) and magnetic north (the direction a compass needle points). I'd figure that having the measurement standard right there would prevent any monkeying around, as the heavy, immovably-placed markers were impervious to theft and vandalism.

The thing I find amazing is that they got the standard setting right. Back in the day, surveyors used celestial observation to set 'north,' which apparently took some time and calculation. The law required the county meridians to be set within one minute -- a sixtieth of a degree -- of true north. My GPS is on the blink and I don't have any other navigational devices, so I wasn't able to test the accuracy of the Flemington markers, but I have to believe they're true.

March 18 starts National Surveyors Week, so it's possible you might find some interesting events at or near any of the county true meridians. Stop by an old county courthouse to find out, and even if you don't find a surveyor, take a moment to face true north.


  1. I've searched for these markers at other county court houses. The markers in Somerset County can be found on the geocaching benchmarking site. I've discovered these markers in Burlington county also, they are unlisted, but there. I had heard the markers in Salem and Sussex were around, but wasn't able to find those on my visits. If any of your readers know of these markers in other counties, I'd love to know which ones.
    Thanks for the article!

    1. Somehow I thought our geocaching readers would like this post! When Ivan and I were in Newton a few weeks ago, we looked for the markers and had no luck. I'm hoping someone out there knows where they are. As we find more (which I'm sure we will now that we know they're out there), I'll be sure to follow up on our Facebook page, at the very least.

      Thanks for checking in!


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