Feature: Return to the River, Part 1, A Proportionate Response
Professional Surveyor Magazine - January 2004
Eric Stahlke, LS
An aspect of boundary surveying, which sets it apart from other modern-day professions, is the use and acceptance of opposites. For example, on one hand, surveyors have great fondness for computers and sophisticated measurement equipment that can produce amazingly accurate results. On the other hand, the use of this equipment is oftentimes employed to replicate work from an earlier era where measurement was an inexact science and errors were endemic.
It is never easy to explain this concept to non-surveyors. Engineers or GIS practitioners willingly discard old methods the moment a better way is found, while surveyors take particular care to preserve their link to the past. The only way surveyors can reconstruct original work, or follow the footsteps of the previous surveyor, is to understand how the work was initially performed. One does not move surveyed boundaries just because one can measure more accurately.
I was thinking about this duality one morning in mid-May shortly after the mailman showed up at our office in Fairbanks and yelled for help with a delivery. In the back of his van was a substantial pile of bankers' boxes weighing somewhere around 200 pounds. Inside these boxes were the records of about 70 surveyed townships, scarcely 30 years old, including original plats, supplemental plats, amended plats, photogrammetric resurvey plats, status plats, several boxes with nothing but field notes, and last, but not least, a foot-high stack of vintage, high altitude aerial photos.
During the next four months our job would be to incorporate this mountain of records into the subdivision of each of those townships, which were scattered like driftwood over a thousand miles of the Yukon and Kuskokwim rivers. These subdivisions would establish final boundaries representing the remaining land entitlements of 14 separate ANCSA village corporations. The methods used to perform this work would have a lot to do with not only the preservation of existing boundaries, but just about everything else that was contained within that pile of bankers' boxes.
Alaska is a big empty place, you can fly in an airplane for hours in any direction and only occasionally see evidence that somebody actually lives here. It might stand to reason that surveying boundaries in a wilderness as vast and empty as this would be as simple as throwing darts at a board. But, as everybody knows, life is far more interesting with challenges and complications. And we Alaskans are always on the lookout for ways to make our lives more interesting.
The survey of Alaska, like most places, was driven by need and circumstance. In a sparsely populated territory, frozen half the year and cut off from the rest of the continent, there was little of either. World War II brought a highway and the need for defense mapping, and the USGS invested a great deal of time and trouble to establish control networks across the wilderness for mapping purposes. However, in relation to its size, Alaska remained largely unsurveyed by the time the extensive oilfields were discovered on the north slope in the late 1960s.
Petroleum companies and state land coordinators suddenly felt the pressing need to establish large oil lease sales and begin the process of fueling an energy-starved nation. But the undetermined status of Native lands in Alaska had to be settled first before any further disposal of real estate could take place. In 1969 the Secretary of Interior, Morris Udall, withdrew all of Alaska from selection in an effort to "freeze" land transfers until legislation could be worked out. Three major political constituencies, the State of Alaska, Alaska Natives, and conservationists engaged in the battle to divide Alaska's unselected lands. The result was the Alaska Native Claims Settlement Act, known as ANCSA, which was enacted by Congress on December 18, 1971.
World's Largest Checkerboard
When the dust settled, the BLM was tasked with a job that Hercules would have ducked, a legislative mandate to survey Alaska. Before the state selections could be carved out, the boundaries of Native lands created by the act needed to be surveyed. This included surveys of more than 16,000 individual Native allotment parcels along with the survey of the extensive boundaries of more than 200 newly created village and regional corporations, all located in remote roadless areas, most requiring helicopter access. The lands were frequently distributed in a salt and pepper fashion, with the large regional corporations restricted to ownership of non-contiguous townships. When the alternating selections were laid on the standard BLM rectangular grid, the world's largest checkerboard was created, about 800 miles on a side.
There was plenty of money available to begin the task, but timing was not good for such a massive undertaking. Construction of the trans-Alaska oil pipeline required hundreds of surveyors and the enticingly high wages that were offered on that project siphoned off much of the available workforce. Added to this was a major catch-22—the corporate boundaries, based on fixed acreages, could not be surveyed until all the individual Native allotments and navigable waters had been segregated out. On the other hand, the survey of the thousands of Native allotments could not begin until years of land exams and application reviews took place.
With no decent options, but awash in funding, the BLM came up with a plan to start by roughing-in the corporation boundaries, with the intention of doing the finish work at some later date when the exact acreage of the inholdings was known and could be subtracted out.
The only problem was that GPS was a distant dream, if that, and there was no practical method available to establish the thousands of miles of boundary line needed. A traditional on-the-ground traverse of this magnitude could not be accomplished in one lifetime.
So the first challenge was to determine what, at a minimum, was required to define these boundaries. A judicial review established that an ANCSA boundary could be minimally defined by the placement of one monument for every two miles of survey. This two-mile monumentation, as it became known, was to be applied to township layout. In other words, an entire township could be surveyed with only 12 monuments spaced at 2-mile intervals around the boundary.
The interior sections would be defined using protracted, unmonumented corners. These computed interior sections would each report an acreage that would provide the basis for an interim conveyance (IC), a type of temporary title that transferred lands to the Native corporations and allowed them to make use of the lands. Patent would come later, when all of the surveying was complete.
Needless to say, this was not a method to be found in the Manual of Survey Instructions, the bible of methodology for the survey and monumentation of public lands in the United States. This venture into uncharted waters was a practical necessity, but also led to much of the confusion and complexity that would eventually be encountered by surveyors in the future.
Next, a method was needed to physically place these monuments without resorting to on-the-ground traverse. The only practical solution that emerged became known as ABC, an acronym for airborne control. A more descriptive term would be intersection, the ancient surveyor's trick of establishing points from remote locations using turned angles. The exact locations of the township and section corners to be established were pre-computed based on statewide protraction diagrams, a computer-generated list containing the mathematical locations of the hundreds of thousands of such corners within Alaska. Then the existing NGS network of triangulation stations, mostly located on mountaintops for visibility, were densified in the areas of survey by use of theodolite and long distance EDM, creating EC (electronic control) stations on proximate hills and ridgetops.
Room for Error
To locate the corners, two or more of the EC stations were occupied by instrument operators with a theodolite, then pre-computed angles were turned to the intersection point where the monument was to be buried. Due to the extensive taiga forests of interior Alaska, this position was rarely visible on the ground. Usually the turned angles were used to guide a hovering helicopter to the point of intersection, then an orange beanbag was tossed out to mark the point on the ground. The pilot, using a special nadir seeking site, would then hover over the bag while the instrument operators turned another set of angles as a check. A day or two later a crew would hike in from the nearest landing area and bury the monument.
There was one problem with this method: it was very hard to perform any decent ground truthing to check if the monument was indeed in the right position. The intersection points could be anywhere from five to ten miles distant from the theodolites, and at ten miles even a quality instrument like a Wild T2 can hide a helicopter with its crosshair. This left some room for error. Years later, when GPS advanced to the level where these monuments could be relocated with precision, the accuracy of the ABC monumentation was found to vary widely. Fortunately, most of the monuments were found to be more or less within limits, somewhere between five and 15 feet from the target coordinate, but a significant number turned out to be clunkers, 50 or 100 feet out. We once found an ABC section corner that was more than 2,000 feet distant from its record position.
Souvenirs for the Bears
Compounding this situation was the fact that many of the monuments were established using a new-fangled drive rod monument instead of a normal steel pipe with flares. The drive rod was a big hit with crews because it was far more enjoyable to set than chipping a hole through permafrost with the heavy spudbar normally used to set a pipe monument. It was also a big hit with survey managers as it doubled production rates. The drive rod, 5/8 or 3/4 inches in diameter, was simply driven into the ground by a gas powered jackhammer to the point of refusal. There was one serious drawback, however, which didn't become apparent until somewhat later. The yearly freeze/ thaw cycle unique to many Alaskan environments worked like a jack ratchet and thrusted these monuments back out of the ground at the rate of about four inches per year. Before long, a sizable percentage of them popped out completely, ending up on the ground as play objects or souvenirs for the bears. Drive rod monuments are no longer used by most surveyors in Alaska, but there was a 15-year legacy of futility before people caught on.
This was the beginning of a number of problems now facing the BLM as the survey program matured. By law, lakes exceeding 50 acres in size, or navigable rivers (don't ask) remain in the State of Alaska ownership, so this acreage is subtracted from Native land claims. Due to extensive permafrost, Alaska is a very wet place. Rainwater and snowmelt do not have the ability to soak into the ground and runoff remains on the surface creating thousands upon thousands of creeks, rivers, and lakes. In the 1970s the only practical and inexpensive method to survey these riparian boundaries was by digitizing existing aerial photographs. Much of the photography used for this purpose was already on the shelf, the results of an earlier USGS mapping project that utilized a NASA U-2 aircraft operating from an altitude of 60,000 feet at various times of the year. Deducing ordinary high water lines from this data was not always easy. Often platted meander lines and reality made poor bedfellows. Another problem is that many Alaskan lakes experience active growth cycles, with the ordinary high water line being a highly elusive and debatable boundary that changes significantly from year to year and decade to decade.
Like a never-ending fractal, complexity soon became a self-generating process. Hundreds of townships across the state were surveyed, platted, and accepted, yet, as time passed, each became subject to an endless series of amendments and corrections. Whenever inholdings were surveyed (a frequent occurrence, given the 16,000 allotment parcels), new supplemental township plats were drafted and filed to amend the acreage and lotting. Problems with the meander line data continually surfaced, requiring new sets of aerial photographs, resulting in photogrammetric resurvey plats. It didn't help that Alaska rivers erode banks faster than hot water running through ice cream. Things eventually became so bogged down and counterproductive that it reached a point where a decision was made to halt the production of the township plats, although the surveys were continued. The legislative mandate was still there, the money kept streaming in, and for another decade a small army of survey crews fanned out over the remote reaches of Alaska, setting thousands of additional rectangular monuments. Each winter, as the crews headed for home, the field notes and data were boxed up and stored for some future generation to deal with and plat.
No Time to Unpack
This future generation was us, and the pile of bankers' boxes in the back of the mail van contained all this history. These 30-year-old townships now required subdivision, the "finish work," to establish the boundaries of each corporation's final entitlement acreage.
The frosting on this giant cake was a recent decision to treat all the ICed land as patented. This meant that all those unmonumented protracted section corners within each township were now to be considered unmonumented true corners, which, practically speaking, since the monuments didnÕt exist on the ground, meant that each was to be computed and reestablished as though it was actually a lost corner, namely by extensive use of single and double proportioning using any remaining ABC drive rods from the township boundaries which the bears hadn't drug off. In other words, it would be our job to preserve the footsteps of a surveyor without feet. And if the ICed land was to be considered patented, then the second part of the equation would be to preserve the riparian boundaries of all riverbanks and lakes as they existed at the date of the IC, 30 years previous, in essence preserving an unknown quantity that used to exist but no longer exists (portions of the Yukon river have moved more than a mile since the IC).
There was a cherry on top of this frosting, there was no time to unpack those boxes to see what was actually in them. Our barge was to set sail in three days, the surveying would begin in a week. It promised to be a very interesting summer.
To be continued…
ERIC STAHLKE is Survey Manager for Tanana Chiefs Conference in Fairbanks, Alaska.
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