Benchmarks
“For any GNSS survey campaign, a proper benchmark is essential to preserve measurement location and elevation. Historically, leveling field operations for second and third order geodetic leveling, provided in the topographic instructions of the USGS, distinguished survey benchmarks as either monumented or non-monumented benchmarks. Monumented benchmarks have a tablet consisting of identifying information surrounding a stamped center point. These marks are represented as a standard metal tablet, disk, cap, or steel rod used to describe the elevation. These tablets are commonly set in concrete, stone posts, firm rock outcroppings, masonry structures, and buildings (U.S. Geological Survey, 1966).” – USGS, Methods of Practice and Guidelines for Using Survey-Grade Global Navigation Satellite Systems (GNSS) to Establish Vertical Datum in the United States Geological Survey
If you get out in the middle of things enough you come across plenty of USGS benchmarks. And lately I’ve been coming across plenty, which is a good sign that I’m getting out there I suppose. Over the last couple of months I’ve come across benchmarks on islands, graveyards (revisiting Thoreau) and on mountain summits. And I’m always thrilled to see them. Benchmarks bear silent witness to facts. You are here, and this is where “here” is. It will remain there, stoic and frozen in time, informing whomever seeks it out.
Many of the summits of New Hampshire feature USGS benchmarks that inform. These metal disk are stamped with the location name, the date of survey and either a triangle or an arrow. The arrows, as you might expect, point you towards the actual benchmark. The triangle lets you know you’ve arrived. Below are pictures of each from Mount Moriah yesterday.
Survey benchmarks let you know you’ve arrived at a place that coincides with the squiggly lines and numbers on a topographic map. Those lines didn’t just write themselves, someone hiked up the mountain and surveyed that land. In the case of the summit of Mount Moriah, it was surveyed at least twice, in 1878 and again in 1958. Another New Hampshire mountain, Mount Tecumseh, was also surveyed at least twice. Like Pluto it suffered the indignity of being knocked down in status. Tecumseh went from just barely a 4000 footer to not quite a 4000 footer. Pluto went from a planet to not a planet to whatever they’ve settled on now. But I don’t believe either cares what we label them. If only humans would learn not to worry about labels as well.
Benchmarks are typical in Civil Engineering, but of course the term has permeated other human activity as well. I suppose I could spend a few paragraphs writing about business-speak terms like benchmarking, but why ruin a perfectly good blog post about the outdoors with business-speak? Get out there and find your way, and celebrate the arrival. Thoreau was a surveyor himself, and like those benchmarks his words silently inform forever for those who would go out and find them. Seek adventure.