Neighborhood Analysis

1. Neighborhood Analysis Meredith Faust Advanced GIS March 27, 2003

2. Neighborhood Analysis • analyzes the relationship between an object and similar surrounding objects. • is based on local or neighborhood characteristics of the data.

3. In GIS, a neighborhood is defined as the field of a cell and its similar surrounding cells.

4. Neighborhood Analysis relies on the use of the Neighborhood Statistics function • Neighborhood statistics is a spatial analyst function • This function computes an output grid where the value at each location is a function of the input cells within a specified neighborhood of the location.

5. Each cell in the following output raster has been calculated by summing the cells in a 3 x 3 neighborhood for each cell • The cells highlighted in yellow identify the neighborhood of the input processing cell with a value of 5 and output cell value of 24.

6. This process is performed on every input processing cell to calculate an output value for each cell.

7. The neighborhood statistic function has several different possible operations: • Majority: Determines the value that occurs most often in the neighborhood • Maximum: Determines the maximum value in the neighborhood • Mean: Computes the mean of the values in the neighborhood

8. Types of Neighborhood Statistics Continued: • Median: Computes the median of the values in the neighborhood • Minimum: Determines the minimum value in the neighborhood • Minority: Determines the value that occurs least often in the neighborhood

9. Types of Neighborhood Statistics Continued: • Range: Determines the range of values in the neighborhood • Standard Deviation: Computes the standard deviation of the values in the neighborhood

10. Types of Neighborhood Statistics Continued: • Sum: Computes the sum of the values in the neighborhood • Variety: Determines the number of unique values within the neighborhood

11. Neighborhood Analysis in ArcMAP • Have the layer that you wish to analyze active in ArcMAP • Under the tools menu, click on extensions • Highlight Spatial Analyst

13. Neighborhood Analysis in ArcMAP Click the view menu Under toolbars, highlight the spatial analyst toolbar

14. Neighborhood Analysis in ArcMAP • Under the spatial analyst toolbar, click the down arrow and highlight neighborhood statistics • Now you are at the neighborhood statistics menu

16. Neighborhood Analysis in ArcMAP • Select the layer you wish to analyze in the “input data” box • Choose what type of analysis (mean, sum, variety, etc…) in the statistic box • Designate the field size and output raster size in their appropriate boxes

17. Neighborhood Analysis in ArcMAP • Wait for the output!

18. What can neighborhood analysis be used for? • To smooth out data from remote sensing errors (minority) • Analysis of land use in a certain area by looking at the surrounding areas and their uses • Counting the number of potential customers for a store in a particular area by looking at surrounding areas

19. ArcMAP Example: • Great Places to go sledding in Charlottesville during the winter!

20. ArcMAP Example: • Start with the cvileedem file • Activate the spatial analyst extension and toolbar

21. ArcMAP Example:

22. ArcMAP Example: • Under the spatial analyst toolbar, click the down arrow and highlight neighborhood statistics • Fill in the appropriate boxes with the values that correspond to your objective

23. ArcMAP Example:

24. Original cvilleedem:

25. Cvilleedem after neighborhood analysis: (maximum)

26. ArcMAP Example: • Areas within the red circles are the maximum elevations within this dem • Therefore, for an intense sledding experience, those areas would be the best!

27. The End! • Sources: • ArcGIS Desktop Help • Erdas Field Guide • www.iwr.msu.edu/edmodule/gis/nieghbr.html

28. Questions?