Research Pays Off - Faster Response After Landslides on Highways: Caltrans Tests Portable Field Mapping Systems
Caltrans engineers previously relied on estimates of landslide geometry and tape measurements from compass bearings to survey land. However, data from maps provided by GPS-enabled systems assist in slope stability analyses and in designing effective mitigation while reducing the response time.
The Caltrans GeoResearch Group (GRG) initiated a research project to test innovative mapping technologies. GRG acquired two field mapping systems and evaluated them during deployments in response to more than 30 landslides from October 2001 through October 2002.
- The first system relied on differential Global Positioning System (GPS) and laser ranging hardware, providing accuracy within 1 meter.
- The second system employed real-time kinematic GPS hardware with centimeter-level accuracy.
- The systems helped produce higher quality data and maps.
- The time required for staff to deliver engineering solutions for maintenance and construction work was significantly cut, reducing the delays to traffic.
- Assuming 200 landslides per year, the mapping system would cost $180,000 to deploy for a 3-year period (200 landslides x $300 labor x 3 years); in contrast, conventional surveys would cost $900,000 (200 landslides x $1,500 labor x 3 years). Even including the initial cost of one mapping system ($15,000) and the cost of the research project ($80,000), the potential net savings would be $625,000 over 3 years (or $208,000 per year.)