Three aspects of the data, species habitat requirements, spatial extent of the occurrence, and the age of the record, are combined to create a probability layer. The layer represents the likelihood of encountering a sensitive species or natural community, based on known sightings, in a given area. Species were grouped into habitat classes. The appropriate habit was extracted from the CCAP land use coverage. Then the spatial extent of each occurrence was used to define a boundary from which to extract the potential habitat. After creating a bounded habitat layer, the age of a record was used to assign a low, medium, or high probability (0.25, 0.50, and 1.00) to the habitat parcel. The probability represents the likelihood that the occurrence still exists. Records prior to 1970 were assigned a low probability. Records after 1982 were given a high probability. Records between 1971 and 1982, by default, were given a medium probability. Each occurrence is also given a biodiversity value, based on the species global status, state status, occurrence quality rank, and the probability value. The greater the threat of imperilment to the species, the higher the value assigned to the occurrence. In a similar vein, the higher the quality of each occurrence, the higher it's assigned value. The biodiversity value of each occurrence is then calculated by adding the values for the global status, state status, and the quality ranking, and then multiplying the sum by the probability value.
The end result is a vector layer of the habitat within each occurrence boundary, with attributes of probability and biodiversity value.