Route 17 Upgrade to I-86 at Exit 131 Laser Scanning

New York State is in the process of converting State Route 17 to I-86. Almost half of the 381-mile length of Route 17 has been designated as I-86, and several remaining sections are either under construction or in the design phase. For the section surrounding Exit 131, NYSDOT Region 8 required a highly detailed digital terrain model (DTM) survey and called on Erdman Anthony for an approach that would leverage the latest technology.

Erdman Anthony recommended combining terrestrial LiDAR to survey the road and highway surfaces with conventional topographic surveying to create a highly detailed and accurate DTM. LiDAR is an acronym for light detection and ranging, also commonly referred to as laser scanning. Terrestrial LiDAR quickly and accurately collects spatial data from a safe location, a feature that made it the perfect field data collection tool for busy highways like Route 17.

Laser scanning emits laser pulses in a predefined array pattern. When a pulse reaches a solid object, it reflects off the object and back to the scanner. XYZ coordinate values are calculated for the point on the object. That coordinate point is assigned an intensity value, based on the strength of the return signal. By recognizing changes in intensity value between points, different materials, such as asphalt, concrete, stone, and paint stripes, can be identified. When all of the points are assembled, they are known as a "point cloud"—and form a 3-D representation of the highway surface with photograph-like quality.

Traditionally, traffic lane closures would be necessary on busy highways like Route 17 while surveyors complete their work. Yet lane closures are costly, requiring an additional crew of highway workers to man flags or set up traffic cones or other traffic-control devices. By eliminating the need for workers to actually enter the travel lane, laser scanning avoids costly and disruptive lane closures.

Following the scan and creation of a point cloud, Erdman Anthony's survey technicians digitized cross-sections at 2-meter intervals along the highway pavement surface. The points were given codes to identify the feature being digitized and then joined to create a DTM of the highway surface. Since cross-sections by traditional surveying methods are typically measured every 15 meters, the resulting DTM was far more detailed.

The end result? The difference between the existing surface and the proposed 3-D model will exceed the latest tolerances in construction technology. In the world of GPS-guided construction machines, contractors can notice even the slightest variation in design cuts and fills. Even an inch or two of variance in materials like asphalt compounds greatly over a multi-mile stretch of highway and can lead to significant cost overruns. By designing off an existing surface modeled from scan data, Region 8 can be assured of highly accurate material bid quantities.

Through laser scanning, Erdman Anthony met NYSDOT's needs by providing a DTM in a safe, highly detailed, and cost-effective manner. Upgrading the highway to Federal interstate standards is expected to create tremendous opportunity for economic development in New York's Southern Tier and Lower Hudson Valley.

This project is the largest terrestrial LiDAR survey completed to date on a NYSDOT project. Erdman Anthony intends to study various technical aspects of the project to reveal recommendations for future best practices. 

Project Details

Location

Woodbury, NY

Owner

New York State Department of Transportation, Region 8

Project Contact

Bryan Merritt, PSM/LS
  • Bryan Merritt, PSM/LS
  • 561-753-9723 x 6017
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