This dataset is a union of seven datasets created by the Merriam-Powell
Center for Environmental Research (MPCER) at Northern Arizona University
using data from a a United States Forest Service (USFS) aerial mapping
project. The dataset was modified by selecting individual species from
the USFS data. The original USFS 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.
More information on aerial sketchmapping is available on the web at:
More information on the digital sketchmap system is available on the
web at: