A Baseline to Remember
|The finished monument at the 0 mark looking down the baseline to the east.|
The Culver-Davies Memorial Baseline in Ohio is a monument to the power of persistence and teamwork.
Sixteen years ago, long before the widespread use of robotic total stations and GPS surveying equipment, a small group of surveyors gathered at some forgotten location. The surveyors were members of the Firelands Chapter of the Professional Land Surveyors of Ohio (PLSO), taking part in their monthly ritual of discussing the issues affecting the surveying profession, the business climate, interesting projects and a myriad of other topics. At this particular meeting, an idea was floated to improve the quality of local surveys and make it easier for area surveyors to ensure the accuracy of their workhorse piece of equipment--total stations. This was the beginning of the Culver-Davies Memorial Baseline--a project that would take one and a half decades and the involvement of multiple private and public agencies to be realized.
Early on, the chapter realized that one of the most difficult issues facing the project was finding a suitable location with the necessary characteristics for a calibration baseline. Historically, many baselines were constructed at airports or along highways that yielded a lengthy, unobstructed view. These locations, though perfect geometrically, can be dangerous or plagued by airport schedules and tight access restrictions that do not allow for safe use and the “let’s stop and do a quick check” type access originally envisioned. The chapter began exploring a local park district for a suitable site. Initially, a bike path in the Lorain County Metro Parks was found to have the necessary length and line of sight characteristics as well as semi-unrestricted access. The site was considered extensively and the park district was in favor of its construction; however, the limitations of not being permitted to take a survey vehicle on the path and the potential for bicycle/survey equipment collisions forced the idea to be abandoned.
|Shane Queer, PS, Ray Foos, PS, Dave Beiter, PE, SI, Scott Hawkins, PS, and Jon Keller, SI pour the top portion of the monuments.|
While the chapter continued negotiating with the Metro Park, another site began to show promise: a long stretch of gently rolling property along the south bank of a reservoir in the Village of New London, Ohio. This site was long enough (almost a mile long), well maintained by the village and easily accessible. The only question was whether the village would allow construction. The answer came in late June 2011, when the chapter approached John Chapin, acting village administrator, with a proposal to construct a calibration baseline along the south side of the village reservoir. Although the chapter expected the idea to be met with reluctance, the village was positive and enthusiastic regarding the baseline’s construction. After listening to a brief explanation of what a calibration baseline is used for and what construction would entail, the village leaders gave their approval. The site of the Culver-Davies Baseline was finally chosen.
The first step in establishing the baseline was to set up a total station and determine the best locations for the proposed monuments. This was done in July 2011 with Dave Conner, Ohio’s advisor to NOAA’s Nation Geodetic Survey (NGS), present to offer guidance. Monument locations were established at 0, 120, 900 and 1320 meters. The typical configuration for a calibration baseline is 0, 150, 430 and 1400 meters. Adjustments needed to be made to the 150-meter monument to avoid a perimeter tile for the reservoir, and the monument at the 430 meter mark had to be set at 900 meters to avoid a large valley that obstructed its visibility from the 0 monument. It is important to note that NGS allows flexibility in the monument locations as long as they are set at 10 meter increments.
After setting hubs at the proposed monument locations, it was Conner’s suggestion to consider building pillar-type monuments for the baseline. A pillar-type monument is one in which the total station is mounted directly on top of the monument. These monuments eliminate centering and leveling errors and make calibrating an EDM faster, requiring less equipment. It is believed that only a few calibration baselines of this type currently exist in the United States. However, the material, labor and cost to construct a pillar-type monument seemed to put this project out of the chapter’s reach.
|Scott Hawkins, PS, and Ray Foos PS, finish the base of a monument.|
A possible solution was to engage the Ohio Department of Transportation (ODOT). The ODOT Office of Cadd and Mapping Services, which oversaw construction of the statewide CORS monuments, had the resources and expertise to assist with the construction of the baseline project. New surveying and mapping specifications adopted in 2011 required ODOT surveyors and consultants to check and certify that their total stations were working properly by measuring a NGS calibration baseline every six months. These checks had to be documented and were to be a part of the deliverables consultants provided with their plan submission. A pillar-type calibration baseline would provide cost benefits and time savings for ODOT’s district, consultants and local surveyors in the north central Ohio area.
The ODOT Office of Cadd and Mapping Services agreed to support the project in any way possible. In the meantime, members of the Mohican-Killbuck Chapter of PLSO heard of the plans for a calibration baseline and pledged their support to the project as well. It was decided that both PLSO chapters would contribute to the cost of the baseline equally and that ODOT would contribute the mount point assemblies and equipment needed to build the monuments.
The Ohio Department of Transpor-tation, two PLSO chapters and the Village of New London coming together to construct a calibration baseline had the potential to be a logistical nightmare. The Firelands Chapter decided that some type of formal document was needed to ensure all parties knew their role in the construction and future maintenance of the baseline. After talking to Phillip “Rusty” Rosebeck, PS, of the Firelands PLSO Chapter, who was a major influence in the baseline project from the very beginning, the group decided to draft a memorandum of understanding for all parties involved to sign. The document grants ODOT and the surveying community permission to construct and maintain a calibration baseline on the Village of New London reservoir property, and gives them free and unrestricted access to the monuments for their use. The Village of New London agreed to maintain the grass and parking areas and to avoid building structures or planting trees that would obstruct the line of sight between the monuments. A clause was also added to ensure that if the monuments on the baseline became a liability issue, both parties had a means of terminating the use of the baseline and the property would be restored to its original condition at the expense of the surveying community.
Design of the monuments and mount point assembly was completed by Dave Beiter, PE/SI, from the Office of Cadd and Mapping Services, along with me and Scott Hawkins, PS, with the ODOT District 3 Survey Department. The base of the monument is a 36-inch-diameter hole drilled 10 feet deep with a #5 rebar cage. The base was poured to grade with Class S bridge grade concrete. A second pour brought the monuments 4 feet above grade and created a trapezoidal shape 2 feet square at the bottom tapering to a 1 foot by 6 inch square at the top. This portion of the monument, which was also constructed of Class S Bridge Grade concrete and had a #5 rebar cage, was keyed into the bottom portion of the monument using a 6 inch diameter by 24 inch PVC pipe. A 6 foot by 6 foot concrete pad was poured around each monument to provide users with a level, solid working surface while they are conducting measurements as well as to keep mowing equipment from damaging the monuments.
|Dave Conner, NGS advisor, checks level on the mount point assembly.|
The instrument mount point assembly is a custom-machined modification of the assembly ODOT uses to mount GPS antennae to their CORS. The assembly consists of a 1¼ inch thick by 8 inch diameter top with three 12 inch posts to anchor the assembly into the concrete. The assembly is machined from Delrin, (Nylon 66), which is a hard and durable type of plastic that can withstand the elements. The center of the assembly has a 6 inch threaded stainless steel sleeve that accepts a 5/8 inch coarse threaded rod used to mount survey equipment to the monuments. This threaded rod has a custom nut welded to it to allow its replacement if the threads are ever damaged. A ¼ inch thick stainless steel wear plate, with custom machined 1 inch flat head screws, completes the assembly and prevents access to the threaded rod and nut. Access to any part of the monument assembly requires special tools to help deter vandalism.
Construction of the Culver-Davies Calibration baseline began in the spring of 2012. Jerry Earl, PS, of the Firelands PLSO chapter and I built the forms for the monuments in May. Plans were finalized, resources gathered and onsite work began in early June 2012. The Ohio Department of Transportation District 3, Huron County Garage, constructed a parking area at the east end of the baseline for access to the monument at 1320 meters. This was the only location along the baseline without existing parking access. The new parking lot will be used by surveyors to access the monument and can be used by the public wanting additional access to the reservoir.
On June 11, Earl, Beiter, Hawkins and I, along with Shane Queer, PS, and Jonathan Keller, SI, also with the ODOT District 3 Survey Department, began constructing the monuments. The monument bases were drilled by the ODOT District 3 Traffic department and were finished that day. The original schedule for this phase of construction was two days with a contingency for a third day. Thanks to the hard work of the individuals involved, we were well ahead of schedule.
|The finished monument at the 1300 meter mark.|
June 12 rolled around with us wondering what to do next. Should we stick to the original schedule of setting forms and pouring the top portion of the monuments the following week, or should we go ahead and set the forms and pour the tops before the weekend? With weather, time and manpower in our favor, we decided to press on with the top portion of the monuments. Earl retrieved the monument forms from his barn while the rest of us scrambled to obtain the necessary 2x4s, form pins and strapping needed to secure the forms to the base sections. The forms were set and secured to the base sections with metal strapping and Tapcon screws. The 2x4 braces were set in four directions to secure the top of the forms in their proper locations. The forms were set using total stations to ensure the monuments were in proper alignment and at the correct distances.
On June 13, 2012, 15 years of talking and two years of planning came to fruition. With the exception of Jerry Earl, who had a prior commitment, the team assembled at the south bank of the New London Reservoir to pour the final portion of the monuments. The total station was set up on the control monument and sighted one last time to check the alignment of the forms, and concrete was ordered. The pouring of the monuments went smoothly with very few glitches. Keller and Queer monitored the forms throughout the pour from total stations set on offset hubs along the alignment and perpendicular to the alignment. Beiter was responsible for getting the concrete in the forms and making sure it was consolidated sufficiently. Hawkins and I set the mount point assemblies in their proper locations and finished the tops. Everyone knew his job, and we all worked well together. Four monuments were completed by noon. For the first time in three days, the group was able to relax and think about what they accomplished. It took hard work and a commitment from all the parties involved to make the Culver-Davies Memorial Baseline a reality.
The pads around the monuments are finished. Final grading and applying a topping compound to the monuments has also been completed. Now, the four 10-foot columns of concrete must “weather” an Ohio winter before the warmth of spring brings a van full of specialized equipment from NGS headquarters to certify and publish the distances between the monuments. It’s my hope that Dave Culver, PS, member of the Firelands Chapter of PLSO and surveyor with the ODOT District 3 Survey Department until his death in 2005, and Dave Davies IV, PS, member of the Mohican-Killbuck Chapter of PLSO and surveyor with the ODOT District 3 Survey Department until he was tragically killed on the job by a motorist in 1993, have some influence with the powers that be to give us a couple of days of favorable weather to certify the baseline named in their memory.