Mapping Methodology

Understanding where at-risk biological resources occur throughout Nevada is the foundation of what the Nevada Division of Natural Heritage does. Knowing precisely where taxa are found and accurately reflecting those locations in our database is of utmost importance and provides the objective scientific data we use to protect resources, enhance development, and reduce the need to list species under the federal Endangered Species Act.

NDNH tracks data using Biotics – a sophisticated relational database rooted in Oracle and using ESRI GIS technology. This system allows the program to capture both locational information as well as a rich set of attributes such as observer, date observed, directions, references, and biological data associated with each observation.

NDNH captures data from a variety of sources including federal agencies, other state agencies, consultants, museum specimens, scientific literature, university studies, and our own field observations. Nevada’s standard for capturing biological data begins with accurately interpreting these sources of information and determining if the information represents a population of that species and includes adequate location information.

If data meet basic biological standards, a source feature is created in a Geographic Information Systems (GIS) database that spatially represents the discrete observation of that particular biological unit or species as points, lines, or polygons with supporting database attributes. Staff biologists map the location to the greatest precision possible based on available information.  However, data are often incomplete, and especially in the case of older data when GPS was not widely available, are sometimes not accurate in their description. To account for this inaccuracy, NDNH adds a field to all mapped features called locational uncertainty. This field describes the area where the observation is most likely found given our uncertainty based on the directions provided, although we put the actual shape in the position we think most likely represents the actual observation. This locational uncertainty is represented as a distance buffer around the source feature.

Once digitized, source features can then be grouped to best represent the local population of that species; this grouping of source features becomes an Element Occurrence (EO). An EO may have one or many source features and is designed to have practical conservation value for the species based on potential continued (or historical) presence and/or regular recurrence at a given location. The EO record then becomes a data management tool that has both spatial and tabular components.  

Every occurrence in the database is subject to thorough quality control reviews by knowledgeable staff. Once entered, data are available for analysis and reporting for a range of purposes from site-specific environmental reviews to statewide conservation planning.

More detailed methodology explanations can be found at NatureServe.