Methodology and Interpretation
RDLEN - Total road length
Total road length by class was calculated by summing the length of all road
classes in the 3 km grid cell reporting unit. Values are reported in meters.
The three road classes included were interstates, highways, and surface streets.
Roads increase imperviousness, potentially decreasing water quality. Roads also
fragment habitat and may act as barriers, especially to large mammals. Wider roads
and higher traffic volumes will generally have more adverse affects, and impact a
larger surrounding area then smaller, less traveled roads.
Quantile: Each class contains an approximately equal number (count) of features. A quantile
classification is well-suited to linearly distributed data. Because features are grouped by the number
within each class, the resulting map can be misleading, in that similar features can be separated into
adjacent classes, or features with widely different values can be lumped into the same class. This
distortion can be minimized by increasing the number of classes.
Natural Breaks: Classes are based on natural groupings of data values. Natural break points
are identified by looking for groupings and patterns inherent in the data. The features are divided
into classes whose boundaries are set where there are relatively large jumps in the distribution of
* EMAP-West Landscape Metrics Metadata (FGDC)