Data are quantifications of real world entities. Information and knowledge are derived from data. Data are at the foundation of all sound decision-making. Huge amounts of data have been, are being, and will continue to be collected to increase our understanding of the natural environment, monitor how that environment is changing, and guide us in making defensible decisions about our management of the environment. Computer information systems allow us to effectively manage and utilize these large volumes of data. Computerized data base systems are a common component of information systems.

In natural resource fields, as well as many other fields, "place" is nearly always an important entity attribute or characterization. For example, we can characterize the physical, chemical, and biological properties of a hazardous waste site, but knowing where that site is located is of equal, or perhaps greater importance. When place is defined in terms of a position on the surface of the earth, the associated data are labeled geo-spatial data. In the abstract, entities are called spatial objects; spatial objects have position attributes in addition to other characterization attributes. For example a contaminated well is located at some latitude/longitude coordinate and likely has numerous associated quantitative descriptors (pH, etc.) of the chemical state of the water it holds. A well is an example of a point spatial object. A river or road is an example of a line spatial object. Real world entities that have area are called polygon data objects.

Analyzing how spatial objects interact is an oft-needed capability when working with natural resource data. Continuing the example above, one might wish to analyze the potential impact of contaminated wells on steam water quality. Locations of wells and streams, characteristics of those wells and streams, as well as other data (soil properties, etc.) would be required to perform such an analysis. A geographic information system (GIS) provides the capability to store, manage, and analyze geo-spatial data. A GIS is often a critical component of a natural resource-based information system. In the assignment below you will complete some very simple geo-spatial data processing tasks using the ArcGIS GIS software package.

A particular data category (e.g. roads, streams) is referred to as a data theme or layer in GIS terminology. Basic GIS analyses involve combining data themes in various ways.

Good decision-making requires good data. Good data have high integrity (were collected by objective means using well-defined protocols) and are timely (represent the current state of the entities being characterized). The timeliness aspect of data is complicated by the fact that data collectors and maintainers can often be widely separated from analysts and decision-makers. The data delivery capability of networks becomes critical in this regard. For data that have general utility, and are often the responsibility of a single government agency, the Internet and World Wide Web has become the medium of choice for timely delivery of the actual data or descriptions of the data to a dispersed audience.

Two geo-spatial data types of high general utility are digital orthophoto quadrangles (DOQs) and digital raster graphics (DRGs). These are both raster (cell based) data types as opposed to the vector data types (point, line, polygon) described above (Figure 1).

Figure 1: Vector and raster data models (from Bolstad, P. GIS Fundamentals : A First Text on Geographic Information Systems, 2002).

DOQs are scans of vertical aerial photographs that have been manipulated in a number of ways so that measurements taken from the resulting digital images are of high integrity. DOQs where each raster represents 1m can be obtained (ordered) for much of the US at the USGS Web site http://edcsns17.cr.usgs.gov/EarthExplorer/. Lower quality images can be obtained directly from TerraServer. A more complete description of DOQs can be found at http://mapping.usgs.gov/digitalbackyard/doqs.html.

USGS has for many years produced topographic maps (via interpretation of aerial photographs) that contain a wealth of information useful in natural resource science and management. DRGs are scanned images of those maps. DRGs corresponding to various map scales can be ordered for much of the US at the USGS Web site http://topomaps.usgs.gov/drg/.

DOQs and DRGs are of such high utility that many state and regional land management agencies make these data directly available over the Internet WWW for their area of jurisdiction. You'll see one of the best examples of that in the assignment below.

Geo-spatial data represented as rasters often result in very large computer file sizes (tens of megabytes). High-speed networks and digital storage media of high capacity are required to efficiently work with such data. Writeable compact disks and ZIP disks are commonly used transportable media (as opposed to diskettes).

You should consider available geo-spatial data for many of the projects you will be assigned in subsequent forestry/natural resources/recreation resource management course work. Also consider taking one or more of the several excellent GIS courses offered in CNR.

Link to the assignment for this week (4.5MB)


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