GPS Saves Clients Money

Several of Yaggy Colby Associates municipal clients have recently been able to take advantage of the newest tool in our surveying department.  The new Trimble R8 GNSS (Global Navigation Satellite System) utilizes all available and imminent satellite signals to quickly obtain precise high accuracy position solutions for data collection.  The system uses what is commonly referred to as GPS (Global Positioning System) to enable surveyors to quickly collect field data in areas that would be very difficult to work in with conventional survey equipment. 

 

With changes being proposed to the FEMA (Federal Emergency Management Agency) flood mapping elevations, several municipal clients needed to act quickly to see how they, and their residents would be affected.  Utilizing the new system surveyors were able to rapidly collect position and elevation data for nearly 100 residences along the Bark River in the Village of Hartland.  Elevation data was also collected on a new bridge that was not included in the calculations that FEMA used in their determination.  The City of Delafield also was able to capitalize on the availability of the new equipment.  Again, the proposed changes to the FEMA mapping were a cause of concern for the City, as well as many of its residents.  Detailed elevation information was obtained for several pertinent features in Delafield, including a survey of the inlet to Nagawicka Lake.  All of this data was then reviewed to see how the revised flood mapping elevations would affect existing the municipalities and property owners.  Yaggy Colby Associates was then able to provide suggestions to their clients as to how to proceed with these issues.

 

Another municipal client was able to utilize this technology to quickly obtain topographic information on several roadways that were part of their paving project this year.  The Town of Oconomowoc required nearly 6,000 feet of roadway to be redesigned due to exacting drainage requirements and then repaved.  Due to the location of these roads, using conventional surveying methods would have required many field days to obtain the information.  However, using the new GPS system, the information was able to be collected in one day.  This included the cross sectioning the existing roadway of the entire project, specific topographic surveying of several low areas, and the location of several benchmark elevations up to a mile away from the site. 

 

The availability of this tool will allow Yaggy Colby Associates to efficiently serve all of our clients with difficult projects, either due to size of project, or location of project, in an extremely cost effective manner.

GPS Technology—WisCORS & the VRS

This year a tremendous tool has become available to those of us in Southeastern Wisconsin. This new technology is a result of many years of planning, and cooperation between equipment vendors, private corporations, educational institutions, and the Wisconsin Department of Transportation. Yaggy Colby is proud to be one of the inaugural users of this technology.

The Wisconsin Department of Transportation (WisDOT) Geodetic Survey Unit is developing a statewide Global Positioning System (GPS) reference station network. The Wisconsin Continuously Operating Reference Stations (WISCORS) Network consists of permanent GPS sites, which provide real-time correctors to mobile users. Mobile users that are properly equipped to take advantage of these correctors can survey real-time in the field to the 2-cm accuracy level.

The first phase of this network has been completed which established 25 permanent CORS in Wisconsin operating east of a line from Marinette to Shawano to Fond du Lac to Madison to Janesville. Corrections are provided in real-time via data packet transmission over cell phones.

Benefits of the CORS Network

· Eliminates the need and cost for another GPS receiver, which acts as a base.

· Eliminates the resource time associated with equipment setup at the base site.

· Enhances security of equipment with no unmanned base sitting miles away from the operator.

· Greatly enhances consistency of coordinate determination.

· Eliminates the need for permanent monumentation on a local level.

· Reliability and redundancy is ensured.

It is important to remember that all standard GPS practices must continue to be utilized just as if we were not using this system. This means that although the surveyor can get out of the truck and start collecting data with the GPS, they still must perform a calibration, and complete their vertical checks. One way to visualize the way this system works is to think of the VRS (Virtual Reference Station) as the GPS base. All functions the base would normally do during a GPS survey, the VRS is now doing. We must still give the software the fixed points on the ground to correlate the information from the VRS to actual survey work.

Calibrations are conducted with points of known coordinates on the ground. The calibration to 4 horizontal points is less than a 30-minute process today. In Southeastern Wisconsin many control monuments can be driven to, which makes calibration easy. The field surveyor can drive to a point, occupy that point for 3 minutes, and then drive to the next point. After this has been completed the survey work can begin.

The VRS system allows survey field crews to conduct data collection and staking in areas that would have been very difficult previously. In addition to opening up additional locations to conduct surveys, we are also able to do so in a highly efficient manner, saving clients money. We are using the VRS to provide surveying services in areas that would have formerly been cost prohibitive, and providing those services in a highly efficient manner.

The CORS/VRS system provides a tremendous advantage to our surveyors and clients. It saves equipment setup time, long complicated traverses, protects our assets, and offers clients a rapid turnaround of data at a reasonable cost. We have doubled our GPS capabilities to ensure that this tool is available when needed. If you have any questions, or are interested in finding out if GPS is right for your next job, please do not hesitate to contact me at davidb@yaggy.com.