time and resources necessary to obtain the new data. If existing data are
selected for use, the key to their success in a modeling project is the documentation and testing of the assumptions that are introduced to the model
by the data.
10.3.2 Spatial Data
Whether searching for spatial data for use as direct model input, calibration data, or ancillary data, one needs to keep the specific purposes of the
modeling effort in mind when selecting data. Generally, one will want to
start simple and add complexity as confidence is developed that the model
and data are a good fit. Using an additive process will help reduce or
manage uncertainty.
In addition to intended use, time and resources will also dictate data
availability. When time and resources are constrained, it is necessary to
work with data that are readily available; however, the danger exists that
scientific questions will then be guided by available data. There is, however,
a plethora of digital spatial data available for minimal or no cost. Valuable
sources of data include the literature (especially the methods sections) as
well as commercial, educational, and governmental data repositories. Many
of these sources are available on the World Wide Web. For example, government sources have satellite data dating back three decades and aerial
photography dating back six decades for much of the United States. Most
data available through federal agencies are free of charge or may carry a
small cost associated with reproduction and media. In addition, many states
offer impressive GIS collections. Good examples include the states of Utah,
Wisconsin, and Illinois. All of the federal land and resource agencies
have websites and offer data for sale or free of charge via the Internet.
Web addresses have not been listed here because of their dynamic and
ephemeral nature.
Good metadata are of special importance with spatial data. The FGDC
was created to develop standards for data collection, analysis and dissemination. Specifically, they have been charged with “developing procedures,
infrastructure, and implementation for a national digital geospatial database” (Lachowski et al. 2000). Further emphasizing the importance of
spatial data standards is the National Spatial Data Infrastructure (NSDI),
the role of which is to coordinate activities regarding spatial data standards
among federal agencies, state and local governments, and the private sector.
10.3.3 Remotely Sensed Data
The increased accessibility of remotely sensed data raises new data issues.
For example, the first major platform of the Earth Observing System
(EOS), the Terra satellite, has five sensors, including the Moderate Resolution Imaging Spectroradiometer (MODIS). The MODIS receives informa190
David Hohler et al.
selected for use, the key to their success in a modeling project is the documentation and testing of the assumptions that are introduced to the model
by the data.
10.3.2 Spatial Data
Whether searching for spatial data for use as direct model input, calibration data, or ancillary data, one needs to keep the specific purposes of the
modeling effort in mind when selecting data. Generally, one will want to
start simple and add complexity as confidence is developed that the model
and data are a good fit. Using an additive process will help reduce or
manage uncertainty.
In addition to intended use, time and resources will also dictate data
availability. When time and resources are constrained, it is necessary to
work with data that are readily available; however, the danger exists that
scientific questions will then be guided by available data. There is, however,
a plethora of digital spatial data available for minimal or no cost. Valuable
sources of data include the literature (especially the methods sections) as
well as commercial, educational, and governmental data repositories. Many
of these sources are available on the World Wide Web. For example, government sources have satellite data dating back three decades and aerial
photography dating back six decades for much of the United States. Most
data available through federal agencies are free of charge or may carry a
small cost associated with reproduction and media. In addition, many states
offer impressive GIS collections. Good examples include the states of Utah,
Wisconsin, and Illinois. All of the federal land and resource agencies
have websites and offer data for sale or free of charge via the Internet.
Web addresses have not been listed here because of their dynamic and
ephemeral nature.
Good metadata are of special importance with spatial data. The FGDC
was created to develop standards for data collection, analysis and dissemination. Specifically, they have been charged with “developing procedures,
infrastructure, and implementation for a national digital geospatial database” (Lachowski et al. 2000). Further emphasizing the importance of
spatial data standards is the National Spatial Data Infrastructure (NSDI),
the role of which is to coordinate activities regarding spatial data standards
among federal agencies, state and local governments, and the private sector.
10.3.3 Remotely Sensed Data
The increased accessibility of remotely sensed data raises new data issues.
For example, the first major platform of the Earth Observing System
(EOS), the Terra satellite, has five sensors, including the Moderate Resolution Imaging Spectroradiometer (MODIS). The MODIS receives informa190
David Hohler et al.