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Home arrow Archives   The American Surveyor     

A Visit to the South Carolina Geodetic Survey Print E-mail
Written by Marc Cheves, LS   
Tuesday, 29 July 2008

A 2.294Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

One of the hold-ups in the implementation of Real Time Networks (RTNs) for machine control has been the vertical accuracies. That being the case, when one of our writers, Joe Betit, told me that he had heard that the South Carolina Geodetic Survey's RTN was achieving vertical accuracies that were acceptable for machine control, I decided to pay them a visit to find out for myself. It was also a perfect opportunity to touch base with longtime acquaintance Lew Lapine, the former director of NGS.

I first met Lew in the early 90s when I was still a practicing surveyor. Lapine had been a National Oceanic and Atmospheric Administration (NOAA) Corps officer for 28 years, having risen to the rank of captain. As the director of NGS, he presided over a rough time for the organization. NGS was facing several challenges: budgets were being cut, the brain trust was retiring and replacements could not be hired, and there was even talk of transferring NGS by dispersing it to the U.S. Geological Survey and the U.S. Forest Service.

During this same time, Sid Miller, the chief of the South Carolina Geodetic Survey, had envisioned a single high-accuracy horizontal and vertical network for South Carolina, and presided over the establishment of the South Carolina HARN. From 1993-95 Miller was responsible for 2,500 miles of 1st Order levels within South Carolina. These level runs were built on work done by the National Ocean Service in the 80s. Everything was blue-booked, so linking the various level runs was possible.

Miller began the South Carolina work with a set of six single-frequency (60-pound!) Trimble SSLs. From there, the SCGS upgraded to 4600s. Today they work with GLONASS-capable R-8s. The NGS had run a 1st Order level line 30 miles inland from the coast and, with the increased demand for accurate verticals due to the threat of hurricanes and sea-level rise, work began to fill in from the line to the coast, paying particular attention to tying in a hundred or so tide gauges on the coast. Miller's most important contribution was the decision to run levels between benchmarks and the HARN and then position many benchmarks with GPS. His efforts resulted in a practical geoid model that could be used to determine accurate orthometric heights from GPS.

In 1998, just as Lapine was presented with the prospect of a change of assignment within NOAA, Miller decided to retire, thereby opening the door for Lapine to assume Miller's position as the head of the SCGS. Under Lapine's leadership, NGS accomplished much, including the establishment of the CORS network, rapid orbits, GPS-controlled photogrammetry, and helping to secure the future of GPS for civilian applications, all things we now take for granted.

Today, as part of a massive height modernization campaign, the SCGS has made GPS observations on more than 3,000 bench marks in 22 of South Carolina's 46 counties. Lapine says that GEOID03 is capable of 1-2cm orthometric heights, as a result of the height mod work they've done. They are also achieving sub-centimeter horizontal accuracies as well. A recent test of 288 of their vertical control points (including many height mod points) resulted in a mean difference (NGS published orthometric height minus 60-second VRS observed value) of ±2mm with a standard deviation (1-sigma) of ±25mm, which includes the contribution of network accuracy of the ±2cm NGS Height Mod Standard). The maximum and minimum differences were 6.2mm and -7.2mm, respectively. A 95% confidence independent of network accuracy and eccentricity was ±15mm.

In response to an RTN need from the SC DOT, Lapine began implementing his vision. An RFP was issued, specifying the operational characteristics of the RTN. Included were specifics such as software operating environments so that it would be compatible with their network infrastructure. Also included was a specification for a system performance of ±1.2cm horizontal and ±2.4cm vertical at 95%. This specification did not include network accuracy. The spatial layout of the stations included as many DOT facilities as possible. There was no leeway to specify fewer than 45 GPS/GLONASS base stations.

Having had a long association with Trimble, Lapine recused himself from the selection process. He suggested adding a state economist to the selection panel, to ensure that the final selection made sense economically for the state. Of three bidders, Trimble was the winner. After demonstrating that it would only take two years to recoup the investment, Lapine was successful in obtaining $1.2 million in SC DOT funding. He is also proud that SCGS, with only 12 employees is able to operate successfully on a budget of less than $800K.

Lapine claims that South Carolina was the first state RTN to incorporate GLONASS observations into its network at every base station. He showed me the stainless steel towers and custom-designed mounts that SCGS uses for its RTN stations. The results of the SCGS approach are that the antenna mounts are stable at the 1-2mm level for the 45 RTN stations.

The hard work of the SCGS is paying off. Under SCGS guidance, orthophotography has been produced for the entire state, with many of the counties having 0.5-foot resolution and 2-foot spatial accuracy for their entire county, while the rest of the state is covered with 1-foot spatial resolution, and 4-foot spatial accuracy. SCGS is responsible for the quality control of the entire set. SCGS stores 6.5 terabytes of orthoimagery!

It has been said that when it comes to non-surveyor users of data, accuracy is addictive. In addition to county use for maintaining tax maps, the biggest group of ortho users is law enforcement agencies. South Carolina law enforcement has a state-of-the-art real-time application. Peanut growers are another group that is demanding ±5cm real time positional accuracy during planting and harvesting, which yields an extra 50 pounds of peanuts per acre.

Another interesting responsibility of the SCGS involves establishing county and city borders. While I was there, they were working on a city limits job, helping a municipality establish its corporate boundaries. Lapine mentioned that the coastal counties now require State Plane coordinates on plats, which fits right in with Lapine's continued modernization of the SC SPC system through the use of GNSS.

Colleagues in many states share Lapine's belief that Height Mod is important. Without a doubt it will enable GNSS to deliver more accurate vertical information. Dru Smith, a geodesist with NGS, believes that to enable a more accurate geoid, the country should embark on a nationwide gravity campaign. But the costs for this exceed $40 million, so perhaps efforts like that of the SCGS are more achievable. Of course, having to run 1st Order levels is costly, but with the modern digital levels, it's not as onerous as it once was.

With skyrocketing fuel costs, trucking companies have started using height information to determine routes with the least gradients. Coastal environment concerns such as sea-level rise, subsidence, storm surges and accurate definitions of state seaward boundaries are also being considered. Lapine pointed out that many federal agencies have a stake in better height information, such as FEMA for flood maps, and the Corps of Engineers for dredging.

When it comes to defense against natural disasters, SCGS is involved in the connection of tidal benchmarks to NAVD 88: the state has some 300 historic gauge sites! Of the 300, SCGS has run 1st Order levels to 208, and of the remainder, some may have been destroyed and others not reachable using traditional leveling techniques. Lapine feels that CORS stations should be co-located with the tide gauges, which would allow ships to become their own tide gauges.

Lapine also says that it is important to only offer services that are economically viable. That is, instead of trying to cover the entire state with accurate vertical information, SCGS focuses on those services that will provide the most benefit to the most people. As he says, applications that result in faster, more productive work are essential.

Author's note: An excellent discussion of the technical aspects of the SC RTN, by Lew Lapine and Matt Wellslager, appeared in July/August 2007 issue of Inside GNSS and can found at
http:// insidegnss.com/node/162

Marc Cheves is editor of the magazine.

Sidebar:
A Life of Service

Cleveland native Lew Lapine graduated from high school in 1965 and started down the road to what would turn out to be a long career in public service. With a penchant for math and science, he enrolled in the Business College at Ohio State University, but soon became bored with the lack of a challenging math curriculum. He looked over the massive catalog of OSU class offerings and learned of a curriculum that included math, science and surveying, and decided to give it a try for a couple of semesters. The rest is history.

While working toward three degrees in geodesy and photogrammetry, he eventually held a variety of positions within NOAA and what is now the National Geodetic Survey. He was in the first graduating underclass for the new Geodetic Science program at OSU. Along the way he became lifelong friends with George Leigh and John Oswald who also became NOAA Corps officers and have had long and successful careers with NGS.

Just after starting his master's degree in 1970, he accepted a commission in the NOAA Corps, a position he would hold until 1998. In 1972 he worked as the chief of a geodetic field party, doing triangulation for the Transcontinental Traverse, which would later become part of the framework for NAD 83. He also worked on the re-survey of the Transpeninsular Line that forms the east-west boundary between Maryland and Delaware. The Coast & Geodetic Survey also performed the re-survey of the north-south line between these two states.

In 1976 Lapine was the operations officer of the NOAA ship Rainier. Two years later he became the chief of operations for NGS. (Author's note: As part of the budget cuts during this period, he was forced to lay off 30 people. Eventually, six of those NGS employees ended up at SCGS.) He returned to sea in 1982 as the executive officer of the NOAA ship Mt. Mitchell. He began work for the National Ocean Service in 1984 and was responsible for developing a national survey and mapping policy. From 1985-87 he was the chief of the management and budget office for the C&GS. He returned to Ohio State University in 1987 to work on his PhD, this time focusing on the use of GPS-in-the-plane for photogrammetry. While in school he became the chief of the photogrammetry division, a position he held until 1993. It was there that he modernized the division and was responsible for both coastline nautical charting and aeronautical charts for airport obstructions. During this time he presided over the amazing explosion of digital sensors, everything from GPS-in-theplane to forward-motion-compensating multi-spectral aerial cameras.

The culmination of Lapine's federal career came in October of 1993 when he became the director of the National Geodetic Survey, supervising nearly 300 employees and managing a budget of more than $31 million. When he became director, the photogrammetry division was transferred to NGS, and the production of all-digital mapping products began.

Lapine's most important accomplishment during his tenure at NGS was the creation of the National CORS and the Height Modernization Initiative. This is where our paths initially crossed. I was surveying in the DC metro area and had the opportunity to use the first CORS station at the National Institute of Standards and Technology (NIST) in Gaithersburg. I soon got to know many of the experts at NGS's Silver Spring Metro Center, and along with that, became friends with Lew.

Lapine's management skills have served him well as he has transitioned to the South Carolina position. In addition to being a licensed surveyor in both North and South Carolina, he is an ACSM Fellow and has received five separate ACSM Presidential Citations. As a public servant, Lapine's work has greatly influenced the way modern surveyors work. It is a pleasure to share his story with our readers. Ever gracious, and always smiling, it is indeed an honor to call him my friend. 

A 2.294Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

 
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