Spatial resolution is a measure of the degree of detail in a spatial data set and has been defined variably as the size of the smallest detectable feature, one half the size of the smallest detectable feature, and the minimum angular or linear distance between detectable features. The specific meaning and measurement of spatial resolution varies widely among disciplines and within geography, depending largely on the application area. The key concepts behind spatial resolution are more generally applicable, however, and are important for anyone interested in the study of spatial patterns and processes or mapping. The following sections outline these major concepts, list measures of spatial resolution commonly used by geographers, and discuss briefly the idea of “optimal” spatial resolution.