1. Definition of Spatial Analysis
Spatial analysis - The process of modeling, examining, and interpreting model results.
Spatial analysis is useful for
evaluating suitability and capability
estimating and predicting
interpreting and understanding
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2. Spatial Analysis - cont.
There are four traditional types of spatial analysis:
Topological overlay and contiguity analysis
Surface analysis
Linear analysis
Raster analysis
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Read more abt contiguity and other analyses

3. Definition of Spatial Analysis
Spatial data analysis involves the application of operations to coordinate and relate attribute data.

4. Spatial Analysis - cont.
Spatial analyses are applied to solve problems related to geographic decisions
Identify high crime area
Generate a list of roads that contribute towards NPS pollution
Selection of a best location for a new business
Determine the spread of nucleotides in underground aquifer
Extent of sage brush infestation in Idaho.
Spread of a disease in western states of US.

5. Definition of Spatial Analysis - cont.
Spatial analysis deals with function and operation interchangeably.
Spatial operations could be applied sequentially
An output could serve as input
Sequence of spatial operations is important
Bolstad, 2005

6. Definition of Spatial Analysis - cont.
Bolstad, 2005
one input can have many outputs
many inputs can have one output

7. Spatial Operations Local operations Neighborhood operations
Global operations
Use only data at one input location to determine value at corresponding output location
: Use data from both an input location and nearby location to have output value
: Use data value from entire input layer to have each output value
Bolstad, 2005

8. Spatial Operations - cont.
Spatial operation types
Selection
Classification

9. Selection Selection operations Examples
Involve identifying features based on several conditions or criteria
The attributes or geometry of features are checked against the conditions or criteria
You can write the selected features into new output data layer
You can use the selection for other analysis
Examples

10. Select: State = Arkansas States = entirely north of Arkansas
States_area>84,000 sq. mi.
States both entirely north of Arkansas and larger than 84,000 sq. mi.
Bolstad, 2005

11. Functions of Spatial Analysis
Conditional selection
Set Algebra
Less than (<)
Greater than (>)
Equal to (=)
Not equal to (<>)
Boolean Algebra
Conditions OR, AND, and NOT
Bolstad, 2005

12. Examples of Expression in Boolean Algebra
Bolstad, 2005

13. Select by Location - cont.
Selecting options
That Meet
That Overlap
That Contains
That are Contained by
That are Entirely Contained By
That are Spatially Equal
That Touch
Click on the white text box to show a list of themes and select the theme that contains the layer you want to query. You can change this later if the layer is not in the theme you select. For the example select Gazetteer
Click on the white text box to show a list of layers within the theme and select the layer you want to query. For the example select Addresses
If you want to display all records of your chosen layer within your chosen boundary accept the default, Display all layer records and if you want to filter the records of your chosen layer within your chosen boundary then click next to Query layer records
This defines how the records you are looking for, the first record set, should interact with the second record set
That Meet: Includes only features referenced by the first record set that meet features referenced in the second record set.
That Overlap: Includes only features referenced by the first record set that overlap features referenced in the second record set.
That Contains: Includes only features referenced by the first record set contain features referenced in the second record set.
That are Contained by: Includes only features referenced by the first record set that are contained in the second record set.
That Entirely Contains: Includes only features referenced by the first record set that completely contain the features referenced in the second record set. The boundaries of the features cannot touch in any way; everything must be interior.
That are Entirely Contained By: Includes only features referenced by the first record set that are completely contained in the second record set. The boundaries of the features cannot touch in any way; everything must be interior.
That are Spatially Equal: Includes only features referenced by the first record set that are spatially equal to features referenced in the second record set.
That Touch: Includes only features referenced by the first record set that intersect features referenced in the second record set.

14. Examples of Selection by Location
States adjacent to Missouri
Bolstad, 2005

15. Examples of Selection by Location - cont.
States containing a portion of Mississippi River or its tributaries are selected
Bolstad, 2005

16. Classification
Categorization of geographic objects based on a set of conditions
Also known as reclassification or recoding
Spatial data operation can be used along with selection operation
Example: classify polygons based on size
Bolstad, 2005

17. Classification - cont.
Classification is an operation to create a new group of classes from an existing set of classes
Classification is governed by a a table or array (decided by user before hand)
Bolstad, 2005

18. Classification - example
Classification of land use for obtaining your required information

19. Classification - cont. Manual classification Binary classification
Example (Last slide)
Binary classification
You need to have two classes
0 and 1
True or false
A and B
Some other two level classifications
Bolstad, 2005

20. Automatic Classification
Good for many classes in one feature file (when it is practically not possible to manually classify into groups)
Requires classification schemes (algorithms or mathematical formula) which will combine various classes into a single group
Equal interval
Defined interval
Quantile
Natural breaks (Jenks)
Standard deviation

21. Classification Examples
Quantile classification
Bolstad, 2005

22. Spatial Analysis Functions
Buffer
Clip or window
Overlay
Intersect
Union
Identity
Near or Distance (proximity)
Dissolve
These spatial analysis techniques in Arc/Info are:
1. Buffer
2. Clip
3. Intersect
4. Union
5. Identity
6. Near
7. Dissolve
The spatial analysis techniques in Idrisi are:
2. Window (clip)
3. Overlay (intersect, union)
4. Distance (near)

23. Buffer one of the most common spatial analysis tools
specific distance representation around a feature 
The distances can either be constant or can vary depending upon attribute values. 
When features are close together, their buffers may overlap. The user can choose to preserve the overlaps or remove them.
The buffer operation creates a new polygon data set

24. Examples of Buffer
Bolstad, 2005

25. Examples of Buffer
So, we really have the same data in both Arc/Info and Idrisi. The Arc/Info coverages are vector, while the Idrisi layers or images are raster.
This slide shows the result of a buffer. In Arc/Info I buffered the roads by 200 units (meters).
I used 200 meters as the buffer distance in Idrisi as well.
[DISCUSS Z-values with Idrisi]

26. Clip or Window
The Arc/Info Clip command extracts part of a coverage using a polygon cookie cutter coverage. To obtain the results shown on the left, I used the roads coverage the Cookie coverage as the cookie cutter polygon.
The Idrisi output on the right is the result of using the Window command. I simply supplied the column and row numbers describing the Cookie layer and created a layer called Clip_Rd.
[VIEW NEXT PART OF SLIDE]
As I mentioned earlier (Intro GIS) often times the most important part of a spatial analysis technique is not the graphic output, but the tabular output.
Let’s take a look at the table created by Arc/Info for the clipped coverage. [essentially the same…just extracted…new length calc’s, etc].

27. Overlay Another common spatial analysis tool
Allows the user to identify areas where features in two layers overlap. 
A new data set is often created from these overlaps. 
In a Union Overlay, all features are included in the new data set but the features that overlap represent a new feature. 
In an Intersect Overlay, only the areas that overlap are contained in the new data set.

28. Overlay Example Analysis Tools select Overlay Intersect tool
Union tool

29. Examples
Bolstad, 2005

30. Overlay Example - cont.
Vector overlay
Bolstad, 2005

31. Overlay Example - cont.
Raster overlay

32. Other Overlay Tools Erase Identity Symmetrical Difference Update
There really is no Identity type of command in Idrisi.
In Arc/Info this command is often used to identify the polygon found at a point location (or series of points). I used this command to identify the vegetation class at each live elk, killed elk, and random location in my graduate research.
This command could also be used to identify the zoning at points throughout a city…or the soil associations at sample points.
Arc/Info
Point coverage
Polygon coverage
What type of polygon is found at this point location?
Boolean or nominal values (overlay polygon coverage and point file)
Polygon coverages for the layers should be overlaid on a point coverage of the grid cell centroids using an overlay process using Identity command in ArcGIS, to assign the environmental or planning geography to each cell in grid. 
Generally, planning and political layers are dealt with in this fashion.
Fractional/Percentage values (overlay polygon coverage and grid cell coverage)
Polygon coverages for the layers should be overlaid on a grid cell coverage using an overlay process using Identity command in ArcGIS, to determine the areas of environmental or planning geography in each cell in the grid. 
These areas can then be summed by grid cell and be used to calculate the percentage of grid cell covered by a particular geography. 
Generally, environmental layers are dealt with in this fashion.

33. Near or Distance
The Arc/Info Near command is used to determine the distance or proximity of all points in a point coverage to point, line, or polygon features in another coverage. Once again, the important information is given not in the resulting geographic features of the new coverage, but in the database table.
[Describe]
[SHOW NEXT PART OF SLIDE]
The equivalent command in Idrisi is the Distance command. Idrisi produces a distance layer with Z-values representing the distance of each pixel to the nearest feature pixel (a pixel having a Z-value >0).

34. Distance Operation

35. Dissolve
Dissolve function’s primary purpose is to combine like features within data layers into new feature
Merge adjacent polygons with same attributes.
DISSOLVE <IN> <OUT> <DISSOLVE ITEM>
We talked about the Arc/Info Dissolve command last week. The syntax of this command is given here.
[Clarify if needed].
In your Arc/Info exercise this week (Ch. 8) you will be practicing with most, if not all, these commands. Therefore, I will let the textbook lead you through the process. However, try to remember what each technique is trying to accomplish…in other words, refer to this week’s and last week’s presentations regarding spatial analysis.
In addition, remember that most of these Arc/Info commands will require three parameters…IN FILE, ‘COOKIE’ or ‘OPERATOR’ FILE, and OUTFILE.
Since we are not using an Idrisi text book, I will show you how to use these techniques, so you can complete this week’s Idrisi exercise.
Are there any questions about the concepts I presented here?
Bolstad, 2005

36. With Spatial Analysis Tools Use What You Can Do?
Find suitable locations.
Find the best path between locations.
Perform distance and cost-of-travel analyses.
Perform statistical analysis based on the local environment, small neighborhoods, or predetermined zones.
Generate new data using simple image processing tools.
Interpolate data values for a study area based on samples.
Clean up a variety of data for further analysis or display.