Spatial statistics

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Spatial statistics

• Topic 4
• 2/2/2007

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What is spatial statistics

• Not like traditional, a-spatial or non-spatial
  statistics
• But specific methods that use distance, space,
  and spatial relationships as part of the math for
  their computations
• Is a spatial distribution and pattern analysis
  tool
• Identifying characteristics of a distribution
  tools used to answer questions like where is the
  center, or how are feature distributed around the
  center? (Measuring Geographic Distributions)
• Quantifying or describing spatial pattern are
  our features random, clustered, or evenly
  dispersed across our study area? (Analyzing
  Patterns)
• Mainly deal with point, line, polygon (vector)
• Why use spatial statistics?
• To help assess patterns, trends, and
  relationships
• Better understanding of geographic phenomena
• Pinpoint causes of specific geographic patterns
• Make decision with high level of confidence
• Summarize the distribution in a single number

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Measuring geographic (spatial) distribution

• Used to
• Compare distributions of different features
• Identify directional trends of features
• Examine changes over time

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Analyzing spatial patterns

• Analyzing Patterns
• Global calculations
• Identifies the patterns/overall trends of data
• Are features clustered and what is the overall
  pattern?
• Spatial Autocorrelation tool
• Mapping Cluster
• Local calculations
• Identifies the extent and location of clustering
  or dispersion
• Where are the clusters (or where are the hot
  spots)?
• Hot Spot Analysis tool

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• Z score is a measure of standard deviation. If
  you have s is (-1.96, 1.96), z score is falling
  between them, you are seeing a pattern of random
  pattern. If z score falls outside, like -2.5 or
  5.4, then you have a pattern thats too unusual
  to be a pattern of random chance

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• Followed with a free ESRI video presentation
  understanding Spatial Statistics in ArcGIS 9 by
  Sandi Schaefer and Lauren Scott.