Photogrammetric Engineering & Remote Sensing

Photogrammetric engineering & remote SenSing Introduction Imagine a national system with the ability to quickly identify forested areas under attack from insects or disease. Such an early warning system might minimize surprises such as the explosion of caterpillars referred to in the quotation to the left. Moderate resolution (ca. 500m) remote sensing repeated at frequent (ca. weekly) intervals could power such a monitoring system that would respond in near real-time. An ideal warning system would be national in scope, automated, able to improve its prognostic ability with experience, and would provide regular map updates online in familiar and accessible formats. Such a goal is quite ambitious -analyzing vegetation change weekly at a national scale with moderate resolution is a daunting task. The foremost challenge is discerning unusual or unexpected disturbances from the normal backdrop of seasonal and annual changes in vegetation conditions. A historical perspective is needed to defi ne a “baseline” for expected, normal behavior against which detected changes can be correctly interpreted. It would be necessary to combine temperature, precipitation, soils, and topographic information with the remotely sensed data to discriminate and interpret the changing vegetation conditions on the ground. Conterminous national coverage implies huge data volumes, even at a moderate resolution (250-500m), and likely requires a supercomputing capability. Finally, such a national warning system must carefully balance the rate of successful threat detection with false positives. Since 2005, the USDA Forest Service has partnered with the NASA Stennis Space Center and Oak Ridge National Laboratory to develop methods for monitoring environmental threats, including native insects and diseases, wildfi re, invasive pests and pathogens, tornados, hurricanes, and hail. These tools will be instrumental in helping the Forest Service’s two Environmental Threat Assessment Centers better meet their Congressional mandate to help track the health of the Nation’s forests and rangelands. We envision two scales of forest monitoring: 1) a strategic, satellite-based monitoring of broad regions to identify particular locations where threats are suspected (i.e., early warning), and 2) a fi ne-scale, tactical tier consisting of airborne overfl ights and on-the-ground monitoring to check the validity of warnings from the upper tier. The tactical tier is already largely in place within the Forest Service and its State collaborators, consisting of aerial detection surveys (sketch mapping from aircraft), ground surveys, and trapping programs. However, these efforts are expensive and labor-intensive, can be dangerous, and may not provide suffi cient broad-area coverage. Far from replacing the tactical tier, the national system will rely on the fi ner-scale efforts to confi rm, validate, and attribute causes of detected forest disturbances. One important objective of the national warning system will be to help direct the focus of the tactical tier, making their efforts more cost effi cient and effective.