CESI is equipped with the latest in Global Positioning System (GPS) equipment which can be used to supplement conventional surveying equipment for your engineering, surveying, and construction projects. By utilizing GPS instead of conventional techniques, surveyors can save time and save their clients money by more rapidly measuring distances and setting points.

Definition of GPS

GPS (Global Positioning System) is a satellite-based positioning system that provides 24-hour continuous coverage to a variety of users. Most people are familiar with GPS units that can be put on cars or golf carts. These GPS units are reasonably priced and provide relatively good positions (within about 30 feet) for most applications. These units determine positions by using the raw broadcast positions of several satellites to compute the latitude and longitude for the location of the receiving GPS unit. The position can then be projected on a map and other computer programs can derive driving directions or other directional information.

How Surveyors use GPS

Surveyors can also use GPS to determine positions. However, surveyors are more interested in relative positions (the distance between different points) than they are absolute positions (where they are on the earth). To determine relative positions, surveyors use a technique called differential positioning. This requires the use of more sophisticated (and expensive) GPS receivers. By using this technique, surveyors can measure very long distances to an accuracy of about one to two inches. The advantage to this method over conventional surveying techniques is the ability to directly measure distances between points without being able to see between them. This can be a big advantage when the distances are very long or when there are many obstacles in the way such as at a construction site.

Applications of GPS

• Horizontal and vertical control for aerial mapping
• Quality control of aerial topography and LIDAR data
• Control for route location surveys (water, sewer, roadway)
• Wetlands mapping
• Utility inventories (water, sanitary sewer, storm sewer, power poles, telephone poles, etc.)
• Construction staking
• Control for land development projects (commercial, residential)
• FCC 2-C letters (tower positioning)

• Greensboro Stormwater Inventory
• FEMA Flood Mapping QC
• Clarkes Creek sewer line
• SC USGS Digital Orthophotos*
• North Carolina/South Carolina state line boundary survey*

VRS Capability / Use for Boundary Surveys & Construction Staking

CESI recently acquired two Trimble R8 GPS System receivers. The dual-frequency RTK, GPS and WAAS/EGNOS receivers offer Trimble’s latest technological solution for producing accurate and reliable survey data. The Trimble R8 GPS receivers provide the capability to utilize North Carolina Geodetic Surveys Network RTK system. The Network RTK system uses Trimble's VRS™ (Virtual Reference Station) system to obtain high-accuracy, real-time kinematic (RTK) GPS positioning for wider areas. The fixed Network RTK system is available at any time without setting up a base station and provides common control wherever you are in the network. Once set up, RTK roving receivers in the field have access to real-time network modeled corrections. CESI utilizes this new technology to extend geodetic control and also to perform construction staking and location surveys in a more efficient and cost-effective manner than was possible with traditional survey procedures and the previous GPS technology.