Letchworth Gorge Trail Improvements

This project involved topographic survey of three specific areas in Letchworth State Park to develop design mapping for the improvement of the Gorge Trail.  These areas had been classified as safety hazards due to erosion over time.  Each area varied in size from less than an acre to over 3 acres, with the entire project totaling approximately 5 acres.  All geodetic control surveys for this project were completed and processed using differential dual-frequency GPS receivers to minimum Second-Order, Class 1 accuracies.

For Area 1, Erdman Anthony completed a detailed topographic survey of historic stone steps.  The Civilian Conservation Corps (CCC) built the steps in the early 1930s.  The slope that the steps were built upon was showing signs of instability, and the steps were beginning to slide into the gorge.  Electronic total stations with data collectors and terrestrial laser imaging were employed to capture the historic steps accurately and measure the magnitude of tilt into the gorge.

Area 2 was the overlook area at the Middle Falls.  Erdman Anthony completed a topographic survey using an electronic total station with data collector and included stone walls and a walkway built by CCC that are above and immediately adjacent to the 90-foot-high Genesee River Falls.  High-resolution ground-based laser imaging was used to capture digital data required to generate the digital terrain model (DTM) surface, with a triangulated irregular network (TIN) documenting existing conditions of the eroding rock face located at the base of the falls.  Use of the high-resolution laser imaging showed that the overlook area was cantilevered out over the gorge by more than 10 feet.  

Area 3 was a trail switchback that was eroding from poor drainage conditions.  A conventional topographic survey was performed in this area using an electronic total station with data collector.  This survey detailed the breaklines and features to aid in the design of a new drainage system for the area.  The topographic mapping and DTM with TIN were delivered in AutoCAD 2000 format, conforming to the New York State Office of Parks, Recreation and Historic Preservation’s CAD specifications.  

A survey report was prepared and delivered to the client for future establishment of the survey control for construction purposes. The combination of conventional topographic survey methods and high-resolution ground-based terrestrial laser imaging proved to be the appropriate combination of technology for this project.  Mapping the gorge walls safely and accurately was of key importance to allow the park’s staff to act quickly to avoid any possibility of future disaster.  This combination also brought a cost benefit to the project by allowing data acquisition to be completed simultaneously, which resulted in being under the proposed budget and in an accelerated timeframe. 

Project Details

Location

Castile, NY

Owner

New York State Office of Parks, Recreation and Historic Preservation

Project Contact

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