CONTINENTAL MAPPING Mapping from Earth, Sky and Spacewww.continentalmapping.com

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In February 2014, the Tennessee Department of Transportation (TDOT) contracted Continental Mapping to map SR 71 in eastern Tennessee to support a road widening project slated to begin in the second quarter of 2014. Redesign of SR 71 was warranted given that the current alignment did not support current driving speeds, there were blind entrances along the roadway and the route had seen significant traffic count increases. TDOT’s desire was to expedite a digital terrain model (DTM) and 3D mapping to support the engineering design process.

To meet that need, Continental Mapping utilized a 3D data fusion process to bring together large scale mapping using low altitude digital imagery and high resolution airborne and mobile lidar. The airborne lidar was essential to characterize the terrain beneath heavily vegetated areas. By

minimizing obscured areas, the airborne lidar reduced the need for ground surveys to supplement the terrain data. Mobile lidar offered a fast and efficient way to survey the dangerous roadway, it offered an

easy way to survey roadway features and pertinent structures, and enhanced the horizontal and vertical accuracy of roadway surfaces.

The project resulted in current 3D mapping and a DTM composed of features hybridized from: photogrammetry, mobile lidar and airborne lidar. Continental Mapping delivered 1”=50’ planimetric mapping, 1’ contours, and a lidar-derived DTM

all at a 0.1-foot vertical accuracy.

LOCATION: Knox County, Tennessee YEAR COMPLETED: 2014OBJECTIVE: Deliver survey grade 3D data with speed and efficiency to expedite design & construction

KEY POINTS: • New airborne imagery and lidar for roadway design • Hybrid photogrammetric and lidar terrain model • Fast-track production schedule expediting 3D data to design team • Digital data produced in project coordinates per TDOT design specs

Tennessee DOT Lidar & Photogrammetry