Spatial Thinking in Planning Practice: An Introduction to GIS

53 Figure 9.9. Is there a spatial relationship between these two layers? Source: GIS Commons. http://giscommons. org/analysis/ - Correlation and regression tests allow you to overlay layers to test their spatial relationship. With both statistical tests, you compute a correlation coe&cient, which ranges from -1 to +1. Positive coe&- cients indicate that the two layer’s variables are associated in the same direction. As one variable increases, the other variable increases (both can simultaneously decrease too). "e values closer to +1 describe a stronger association than those closer to zero. A negative coe&cient depicts two layer’s variables that are associated but in opposite directions. As one variable increases, the other variable decreases. Values closer to -1 have a strong negative association. If the correlation coe&cient is near zero, there is little to no association. Both of these pro- cesses are raster based. "is chapter material has been collected from the following web links that holds information with CC copy- rights: use and share alike. http://giscommons.org/analysis/ http://2012books.lardbucket.org/books/geographic-information-system-basics/s08-01-raster-data-models.html https://www.e-education.psu.edu/geog160/node/1935 http://2012books.lardbucket.org/books/geographic-information-system-basics/s12-geospatial-analysis-ii-raster-. html Discussion Questions 1. In what ways does a raster analysis provide insights that may not be available through the vector data model? 2. What is an urban and regional planning application where map algebra could provide insights helpful for characterizing a location? 3. As a practicing planner, how might you integrate the advantages of vector and raster data models when engaging the public? Chapter 9: Raster Data Models