Surveying tool's new direction


Locators: Bench marks, small metal disks affixed throughout the country's landscape, still come in handy in the era of satellite positioning.

July 10, 2000|By Candus Thomson | Candus Thomson,SUN STAFF

Surveyors need them, but hikers crave them.

Bench marks, those 3-inch metal disks embedded in the rocky tops of many mountain summits, are the second thing many hikers seek when they reach the top (after they take in the view).

When accompanied by the obligatory thumbs-up summit photo, the bench mark proves a hiker's mettle while also supplying pertinent information: longitude, latitude and altitude.

No one has a precise count on the number of bench marks in this country. The best guess is more than 3 million, hammered into rocks, buildings and bridge abutments by a number of federal, state and local agencies.

You'll see them on Pikes Peak in Colorado and the Bromo Seltzer Tower in Baltimore.

A woman in Minnesota has even turned bench mark replicas into a home business whose motto is: "Know where you are. Be where you're at."

While the popular Global Positioning Systems have made surveying easier by using satellite data as references, they haven't made bench marks obsolete, says Jon Campbell of the U.S. Geological Survey.

"These markers have a new role. They provide a control point to let surveyors and hikers know how accurate their GPS hand-held units are," Campbell says.

The whole survey thing dates back to Thomas Jefferson, who as president established Survey of the Coast in 1807. With an initial equipment budget of $25,000 the agency's first task was surveying New York City and the New Jersey suburbs.

It wasn't long before Jefferson sent Lewis and Clark westward and demanded a more accurate picture of the country's interior.

By 1843, the agency, renamed the Coast Survey, had moved up and down the East Coast, setting up surveying bases on Kent Island in Maryland and in Massachusetts.

In 1878, Congress renamed the agency the U.S. Coast and Geodetic Survey and 21 years later dropped the "U.S."

More recently, the organization was made part of the National Oceanic and Atmospheric Administration in Silver Spring and given the name National Geodetic Survey (NGS).

Donna Amoroso, an NGS technician, estimates that the agency's surveyors have installed more than 800,000 markers over the years, with one or two "field parties" still out in the countryside, placing new markers and replacing damaged and stolen ones.

"We've got markers set in the ground from the 1800s, mostly near the coastline," Amoroso says.

Even though bench marks are sunk deep into rock or a structure to make them as permanent as possible, they're not.

Markers get damaged or destroyed when subdivisions are built or farmers plow fields. Others call NGS to demand the disks be removed.

"Just last week I got a complaint from a property owner. If it has to be moved, we'll move it, but a lot of people just pull them up," she says.

Some people gouge them out for souvenirs, despite an inscribed warning that damage or removal is subject to a $250 fine.

Amoroso says NGS doesn't make good on its threat. "It's not worth our time or effort to prosecute."

Global Positioning Systems have not diminished the need for NGS bench marks, because "you'll always need a reference point," she says.

While NGS is still putting markers in the ground, another major federal agency has reached its limit.

The U.S. Geological Survey (USGS), charged with designing topographical maps, doesn't need more of its own bench marks, according to Charles Henkle, who installed hundreds of them from Maine to Florida from 1961 to the late 1970s.

"We pretty much have gotten out of the business," says Henkle, now a USGS consultant working on a mapping project in the Everglades. "It has gotten awfully expensive."

USGS went into the business in 1879 when it was authorized by Congress as part of the Interior Department. (NGS is part of the Commerce Department.)

Lawmakers wanted better maps and an inventory of the country's timber and mineral rights in the 1.2 billion acres west of the Mississippi River.

In addition to serving as a mapping reference point, the bench marks proved that USGS employees had visited a particular point, much the way a night watchman punches a time clock on his rounds.

USGS surveyors had their hands full, with cattlemen fighting farmers over land in the Great Plains and miners battling over mineral stakes.

Still, they drilled and sank thousands of disks throughout the West.

Henkle and surveyors of the modern era have better tools, but more exacting standards means installing bench marks so they don't shift and "corrupt" the position.

After choosing the location for a bench mark, surveyors drill a hole and then use a power hammer to drive precast, 6-foot-long steel rods into rock or other structures to the "point of refusal." The disk is installed as a cap on the top of the rod.

"In many instances, you'll find the cap is stolen, but the rod is still there," he says, laughing.

Henkle has installed bench marks in Antarctica, where the weather is brutal but, "you don't have to worry about people, trees, traffic or bureaucracy."

Betty Risser was lost.

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