Benchmark Hunting

Dec 24, 2009 by Jared Smith

I got a GPS for Christmas. Being unable to wait until Christmas, I’ve been playing with it for a week or so. I’d like to do some geocaching, but with all of the snow, it’s not really the best time for it. Instead, I read up a bit about benchmark hunting. In short, it’s like geocaching, but you look for old markers and monuments instead. Most of the markers are official government surveying markers that were generally placed in the 1930’s, though some are much older. They are typically metal disks embedded in monuments, bridges, roads, mountain tops, etc. You’ve probably seen one before – there are over a million of them in the United States.

When placed by surveyors in the 30s, their elevations and/or coordinates were very accurate. In fact, if you compare the original 1930’s measurements with super accurate modern GPS equipment, most are within an inch or so. However, the positions of most benchmarks that record elevation were only generally described in the 1930’s or 1960’s. The latitude and longitude coordinates for most of these are just rough guesses based on comparing the text location description to a map. Benchmark hunting involves using a GPS, old general descriptions, and a bit of luck and skill to try and find the original markers. Once found, you can log your finding and the marker condition to help the government and surveyors know if they can be utilized in the future.

As a Christmas Eve activity, Abbie and I researched a few interesting benchmarks to go look for. The coordinates we had were only accurate to within 1/4 mile or so. And most of the descriptions reference things from the 1960’s that are no longer there – such as old fences, telegraph poles, etc. With the GPS, the descriptions, and some big winter boots, we set out on an adventure to see if we could find them. We went four for four!

Our first benchmark was described as being embedded in the foundation of an old building. Luckily the building (the Trenton Feed Co-op) is still standing (barely).

The benchmark was originally 6″ above ground, but as the parking lot was improved and added to, it is barely visible today. We had to dig a bit to see all of it.

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The next benchmark was buried in a rock outcropping in a field. It took a bit of digging around to locate it.

We went on to find two more after 1/4 mile hikes along some rail road tracks.

Anyway, we both had a wonderful time and have likely found a new hobby. I enjoy using geeky technology and old fashioned ingenuity to try to find old stuff and Abbie is excited to find more treasure markers.