Web Exclusive! Known Positions

December 1, 2007
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Before surveyors could chart depths, they had to fix heights

The familiar Coast and Geodetic Survey disks are often set into granite on hilltops.
photo: Catherine Schmitt


On the coast of Washington County, a small hill rises between Pigeon Hill Bay and Dyer Bay. The 317-foot summit is marked by a cairn of stones; beneath the stones is a copper bolt driven into the exposed granite, marking an 1856 visit by the Survey of the Coast, the first scientific agency created by the U.S. government.

The Coast Survey is the predecessor of the National Geodetic Survey, which today is part of the National Ocean Service, an office of the National Oceanic and Atmospheric Administration (NOAA). NOAA also includes Sea Grant, the National Marine Fisheries Service, and the National Weather Service. NOAA is commemorating the 200th anniversary of the Coast Survey throughout 2007.

Two hundred years ago, there were no roads, no highways, no extensive rail network. Shipping occurred via the coast, which also hosted a huge commercial fishing industry and provided the route for foreign trade, correspondence, and travel. Yet despite the importance of marine navigation, few charts were available and shipwrecks were common. Finally in 1807 President Thomas Jefferson created an agency to provide nautical charts for America’s growing ports and busy coastline.

After a delay caused by the War of 1812, the first work of the Survey of the Coast began in the Hudson River Palisades region of New York. By 1850, survey parties had reached the southern Maine coast.

Surveyors needed to use a common reference system so that maps and charts would align with one another, and they also had to establish known positions on land before they could position survey vessels at sea to measure the water’s depth. The early work of the Coast Survey involved scouring the coast and inland regions of Maine to establish these reference points and continue the survey that began in New York and arched south and north along the East Coast, in what’s known as geodetic surveying. Vertical reference points, or benchmarks, for elevation were placed on the coast, relative to sea level. Only after benchmarks and horizontal control points called triangulation stations were established did the Coast Survey begin hydrographic surveys, mapping the shoreline and charting the bottom of rivers and harbors.

Because the survey covered such a large area, the curvature of the earth had to be factored into distances and angle measurements. A wide variety of techniques are used in geodetic surveying, including triangulation and astronomical observations for determining latitude, longitude, and direction.

An ambitious young scientist of the time would have had few permanent landmarks to use in orienting any map - there were islands, mountains, lighthouses, churches. Inland triangulation stations often followed high ridges to assure developing lines of sight of 20 to 40 miles between stations. If the angles between three points were known, and the distance between two of the points was known, then the distances to the other points could be calculated - basic trigonometry applied at a landscape scale. The mountains in Maine were well-positioned for triangulation, and stations were established on high points along the coast as well as the more inland hills of Mount Pleasant, Mount Blue, Mount Harris, Thomas Hill in Bangor, and Bald Mountain in Dedham.

Once stations were selected, permanent monuments were placed at the site - a hole drilled in granite, a copper bolt driven into ledge, a buried brick. Later markers would employ a cast brass disk stamped with the station’s name and observation date. A distant observer would make angle measurements between the new station and an established one, pointing a high-precision telescope on a distant target called a heliotrope that uses a mirror to reflect sunlight in a precise luminous point visible from miles away.

A “lightkeeper” would stand on top of Pigeon Hill with the heliotrope, reflecting the sun’s rays back to another surveyor in Mount Desert, Beddington or Bucks Harbor. Sometimes mountains were observed from great distances; Peaked Mountain in Clifton (known locally as Chick Hill) was observed from Mount Blue, over 92 miles away.

“No one today would suspect the enormous effort of surveying, mapping, and charting that went on in Victorian Era Maine,” says survey historian Harold Nelson with the Maine Department of Transportation’s Property Office.

Much of this work was carried on under the direction of Prof. Alexander Dallas Bache, who was appointed superintendent of the Coast Survey in December 1843. Born in Philadelphia in 1806, Bache was the great-grandson of Benjamin Franklin and a graduate of West Point. He served three years in the Army Corps of Engineers and then taught natural history and chemistry at the University of Pennsylvania. During his term with the Coast Survey, Bache helped form the National Academy of Sciences and serve as its first president.

Other notable Coast Survey employees from this period included Alexander Wadsworth Longfellow, brother of Maine’s poet Henry, who ran a topographic party in the 1800s and even used the chimney of the family home in Portland as a triangulation site, according to Nelson.

Under Bache, the Coast Survey progressed eastward, monumenting Ragged Mountain, Isle au Haut, Mount Desert, and Pigeon Hill. Crews then ventured inland through the sandy barrens and granite promontories of Downeast Maine, laying a baseline in Epping Plains and marking the summits of Tunk (“one of the most inaccessible stations on the coast of Maine”), Humpback (Lead) Mountain, and Cooper Hill.

At Calais, a temporary astronomical observatory was built for determining longitude: using telegraph wires, observers recorded the time span between when a star passed over Calais and when the same star passed over Bangor, the next astronomical station to the west. Since the earth rotates 360 degrees each day (24 hours or 1,440 minutes), the time difference between the two observatories reveals how many degrees separate them…and so time becomes space.

“Bache knew that at some time there would be a telegraph connection across the Atlantic, so he pushed the longitude network eastward, Harvard to Bangor in 1851, Bangor to Calais in 1857,” says Nelson. With the successful laying of the Transatlantic Telegraph Cable in July 1866, the Coast Survey sent men to Calais, Newfoundland, Ireland and Greenwich, England, to make the longitude connection complete between Greenwich and North America. On Dec. 16, 1866, observations of stars passing above Calais completed the connection work. It is to geodetic surveying and mapping what the “golden spike” was to the railroad, says Nelson.

Today, the remains of the observatory can be viewed in downtown Calais, across from the Dunkin’ Donuts, on a small, park-like hill. Atop this hill is a tall granite post that local kids call The Chimney. In July 2005, NOAA set a commemorative survey disk at the observatory site, marking the first site in NOAA’s Heritage Trail.

Throughout the 1900s, survey crews would revisit old stations, and their notes read like an epitaph of the Maine landscape, as fields became forests and pastures disappeared beneath pavement.

The station at Mount Agamenticus was established in 1847. Over the next half-century, the station became surrounded by trees, and a new, visible mark had to be placed by 1908. In 1943, a military reservation “of considerable size” occupied the summit, by 1965 the mountain had become a ski resort, the military radar tower replaced with a parking lot. Holman Point, near Fletcher’s Neck in Biddeford, was established in a rocky pasture field in 1868 but a golf course erased it in the following century. Butland Island was marked in 1867 with an upside-down glass bottle sunk in the ground and a pile of stones; by 1928 the land was “covered densely by modern buildings.” Such was the fate of many southern Maine survey stations. At Seal Head Point, the station mark was placed in 1851 near “a lone elm tree, which is visible from a great distance;” 100 years later both the elm tree and the mark were gone. Another mark became the site of Bucks Harbor Air Force Station and was covered by a radar dome. Stations in church steeples and hotel cupolas were lost when buildings burned or were torn down. Other marks simply were never found again.

Many the 1850s survey marks that survived became part of the National Spatial Reference System, a national geodetic control network managed by NOAA that provides today’s surveyors and navigators with a consistent coordinate system for position (latitude and longitude), elevation, distance and direction between points. Modern technologies of Global Positioning Systems allow one point to be used for both position and elevation, says Curt Crow of the National Geodetic Survey, but GPS and satellites would be useless without the comprehensive foundation of maps and charts established by the Coast Survey in the 19th century. Today’s nautical charts retain many of the same characteristics and coverage as the Coast Survey’s earlier editions.

The Coast Survey is responsible for our red-right-returning buoy system, as well as many other notable feats, including the discovery of Stellwagen Bank and Nantucket Shoals and the first major study of the Gulf Stream.

For anyone who uses nautical charts or a handheld GPS unit, the work of the Coast Survey is worth more than just a passing acknowledgement. They were the true chroniclers of the coast of Maine, back when man followed the stars to determine the hour, and climbed mountains to understand his place in this world.

"This article was first published in the August 2007 issue of Working Waterfront."

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