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Home arrow Archives   The American Surveyor     

A Line Runs Through It - PLSC Supports New 40th Parallel Exhibit Print E-mail
Written by John B. Guyton, LS   
Sunday, 15 March 2009

A 2.208Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

The northern Front Range of what is now Colorado was a pristine wilderness well into the 1850s, trampled only by a small number of trappers and explorers, and by the light footprints of native peoples who had inhabited the area for over a millennium. These halcyon days changed quickly with the discovery of gold in nearby Golden, resulting in thousands of settlers moving onto public domain lands that had not yet been surveyed.

In 1859, the land at the mouth of Boulder Canyon was officially established as the Boulder City Town Company. It was located north of the 40th parallel in the Nebraska Territory; the land to the south of the 40th parallel at this time was in the Kansas Territory. Colorado statehood was to come 17 years later.

Extending the 40th Parallel Westward
The General Land Office was under pressure to extend the Baseline to the west from the 6th Principal Meridian. On June 10, 1859, U. S. Deputy Surveyors Jarret Todd and James Withrow were awarded the contract to extend the baseline to the summit of the Rockies, starting 204 miles west of the Missouri River, and making their way across the plains until arriving in Boulder City on August 31 of that year. In September, they pushed the line all the way to the top of what they believed was the summit of the Rockies, setting a cairn pile and various accessories, including a cross that they chiseled into a knife-edged ridge. On the west side of the ridge was chiseled the word "Utah," which at that time was the point of terminus for the Kansas and Nebraska Territories. This chiseled cross on the rock face precipice was rediscovered by Doyle Abrahamson, Geof Stephenson, USGS geochemist Dr. Peter Modreski, Jerry Penry and a team of three other surveyors and mappers in the summer of 2006. This exciting rediscovery is chronicled in articles that appeared in the Denver Post and The American Surveyor. Links to both can be found on the home page at www.plsc.net.

The 40th parallel of latitude is closely aligned with Baseline Road in the contemporary city of Boulder. The actual baseline in the Boulder area that was established by Todd and Withrow is approximately one-half of a second of latitude (about 30 feet) north of the actual 40th parallel, astonishingly precise, given the terrain and the instrumentation available in 1859.

Preparations are underway for events in 2009 to commemorate the 150th anniversary of Boulder's founding. This sesquicentennial, coincidentally, is also that of the Todd & Withrow survey.

Dedication to Early Surveying
When the City's transportation planners were designing a new bus stop and bicycle path on Baseline Road, just east of Broadway, artist and designer Christian Muller conceived the idea of marking the existence of the line and increasing public awareness of its significance. He designed a monument and plaque dedicated to the accomplishments of the early surveyors. A bright red concrete line that is aligned with the baseline is permanently embedded in the sidewalk. A colorful world map appears on the concrete pad at the bus stop, showing the location of the 40th parallel. A huge 25,000-pound boulder, found high in Boulder Canyon, was selected, carefully split in half, and placed to the east of the bus stop so that the red line appears to bisect the gap (see photos). This gap is illuminated with red LED lights after dark, giving it a brilliant glow. "Rocks are timeless," says Muller.

The monument is designed so that the smooth, interior surface that faces the heavily traveled road and path to the north is inscribed with the diagram of a surveyor, designed by Boulder County artist Gaynor Nelson. The story of Todd & Withrow, researched and composed by Boulder County Surveyor Jason Emery, is inscribed and concludes with, "This stone marker, set along the `Baseline' as surveyed in 1859, celebrates the historic survey party as well as all surveyors whose remarkable work aided in the organized westward expansion of the United States."

The south-facing surface that faces the busy BaseMar shopping center includes two brass plaques. Fifty percent of the project was funded by private donations, while the other fifty percent came from the City's Transportation Division and the Boulder Arts Commission. In 2007, the Professional Land Surveyors of Colorado (PLSC) donated $3,000 to the $38,000 project, and is permanently recognized on the contributors' plaque.

The donation by the PLSC was made as an educational effort, to increase awareness of the existence and importance of the surveying profession. The monument appears to be fulfilling its intended role. The bike and pedestrian path connects the university campus with a large shopping and residential area of Boulder, and many people have been observed coming to a full stop and taking the time to look at the rocks and read the inscribed story of Todd & Withrow. It is also a tempting rock to climb for passers-by of all ages.

Accessible Geodetic Control
During the design phase, Boulder Transportation Program Manager Alex May, Kurt Ernstberger and I had the additional idea of placing a working geodetic control point on a raised, stone bench next to the split boulders that can then be submitted to the National Geodetic Survey (NGS). The brass marker would be highly visible to the public, increasing overall interest in the monument, and the working control point in such a unique setting would be of interest to local surveyors. Traditionally, the NGS bluebooking process of data collection, processing and data submission could take months or years to complete.

As things have changed in surveying since the days of Todd and Withrow, so have NGS procedures to process and submit data. NGS has developed a program called Online Positioning User Service (OPUS) that utilizes the internet and the National Spatial Reference System. An excellent introduction to OPUS can be found in an article written by Dan Martin, NGS Geodetic Advisor for the State of Vermont titled, "OPUS Rapid Static," published in the April 2007 issue of The American Surveyor. In summary, OPUS is a web-based application that allows a user to submit a minimum of two hours of dual frequency GPS data that automatically gets processed relative to three stations within the Continuously Operating Reference Station (CORS) network using NGS PAGES software. The resulting coordinates will generally have a network accuracy of two centimeters or better horizontally and three centimeters or better vertically (ellipsoid height). The user will receive this information in the form of an e-mail, normally within minutes of submittal.

However, NGS is currently beta testing a newer version, currently referred to as OPUS Data Base or DB, that will allow your OPUS-computed position to be stored as part of the NGS database. To view the background, instructions and currently posted datasheets, go to http:// beta.ngs.noaa.gov/OPUS There are several requirements, in addition to using dual frequency receivers. It requires 4 hours of data, it must be well monumented (stable, permanent, unique, recoverable and safe), it must include photos as specified by NGS, a full description of the monument is required, including how to reach the mark, and it must achieve: >/= 90% observations used; >/= 80% ambiguities fixed >/= 0.02m peak-to-peak horizontal </= 0.04m peak-to-peak vertical.

All versions or flavors of OPUS require accurate antenna heights and the NGS calibrated antenna type must be identified. As in any GPS observation, observing longer and choosing the right time to observe improves your accuracies. For height, the ellipsoidal height should compare well with post-readjusted (NSRS 2007) positions for surrounding control. The orthometric height is dependent on the geoid, thus not as accurate as leveling to nearby vertical control benchmarks.

Kurt Ernstberger of Flatirons Surveying in Boulder, and Treasurer of the Central Chapter of the PLSC, conducted the required field observations on the geodetic control point in the monument bench on January 28, 2009 and uploaded the 4-hour data to NGS. The data sheet was posted for public use the very next day. It includes an expandable photo of the monument (stamped "Todd & Withrow 1859 Baseline Survey"), an additional photo of the site on the day of the data collection, a complete description of the site and location, and a table of the data.

This was the very first OPUS DB monument and data sheet posted for the State of Colorado. "Posting data to this web-based system was very easy--more surveyors should really start doing this," said Kurt. "The more surveyors contribute to this, the more we will all benefit. I hope that the NGS will make this beta test site a permanent feature."

Technology such as GPS has surely improved the time it takes to get final results; however, the underlying concepts of surveying are similar to the days of Todd and Withrow. But the juxtaposition of this very latest technology with a monument detailing the westward journey of Todd and Withrow so many years ago makes this exhibit particularly interesting to the public and to surveyors alike.

150 Year Celebration Plans
A dedication ceremony for the monument will be held this month on March 20th, coinciding with National Surveyors Week. It is hoped that this event will be an informative "handshake with the past" by bringing publicity to the past accomplishments of surveyors like Todd and Withrow and will also highlight the present and the future of our ancient and noble profession.

John (JB) Guyton is the CEO of Flatirons Surveying & Engineering in Boulder/Longmont, CO. He is the current editor of PLSC's magazine, Side Shots, and represents Colorado in the Western Federation of Professional Surveyors.

A 2.208Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

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