Airborne laser terrain mapping for expediting highway projects: Evaluation of accuracy and cost

A typical highway project generally takes 5 years or more from planning phase to construction stage, particularly in wooded and difficult terrain using traditional topographic terrain mapping methods. This paper presents an application of airborne laser terrain mapping technology for a 9 km (5.9 mi.) long highway project in a difficult densely wooded terrain with steep slopes and ravines. Elevation data accuracy, efficiency, and cost effectiveness were compared with the traditional aerial photogrammetry and ground based total station survey methods. The elevations of centerline and 15 different cross sections were compared with groundtruthing data from the total station survey. Using appropriate flight mission parameters, the airborne laser technology permits elevation accuracy of 0.13 m (5 in). There are less operating constraints which adversely affect the productivity of traditional methods, such as cloud and vegetation cover, time of day, and intrusion into private properties. It is recommended to combine the low-altitude airborne laser technology with centerline staking by total station survey and aerial photography. The recommended combined approach saves 33% of the budget and 35% of time.