This dataset is a compilation of forest insect, disease and abiotic damage mapped by aerial detection surveys on forested areas in the United States. At this time, the National Aerial Survey Data Standards require only mortality and defoliation data be collected and reported. However, many cooperators collect data on other types of damage and therefore, the national database has been designed to accommodate these data. Low-level flights, typically 1,000 to 2,000 feet above ground level, are used to map forest damage. Observers use paper maps, typically 1:100,000 scale USGS maps, upon which they record the damage. There is also a digital sketchmap system that may be used. The digital system uses GPS to display the plane's current location on screen along with an electronic version of a variety of base maps. It allows the observer to record damage areas directly in a GIS database. Due to the nature of aerial surveying, there may be areas within the delineated polygons that are unaffected. For example, an area with a patchy mosaic of forest insect activity may be recorded as one larger polygon by the observer. During aerial surveys, only fading trees (those with yellow, brown, or red foliage) or those with some defoliation are mapped. Older dead trees which have lost their foliage or have dull colored foliage are not typically mapped for two primary reasons: 1) it is harder to see older dead trees that may have lost their needles and 2) it prevents recording trees that were mapped in a prior year's survey. Overview surveys are a 'snap shot' in time and therefore may not be timed to accurately capture the true extent or severity of a particular disturbance activity. Specially designed surveys with modified flight patterns and timing may be conducted to more accurately delineate the extent and severity of a particular disturbance agent. Special surveys are conducted when resources are available to address situations of sufficient economic, political or environmental importance.
