GST 101 Introduction to Geospatial Technology��Unit 7 – Introduction to Spatial Analysis�Module 7.1 –Basic Spatial Analysis Techniques����� � �

Ann Johnson

Associate Director

ann@baremt.com

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Based upon work supported by the National Science Foundation under Grants DUE 1304591, DUE 164409, DUE 1700496, DUE 1937177, Due 1938717 DUE 1937237, 2030206 and 2015927. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

What is Spatial Analysis?

• The processes of extracting or creating new information from geographic features and their attributes using operations or functions to investigate the spatial relationship between locations and attribute values
• Operations or functions can be used on spatial feature locations or their attribute values using data from vector, raster and other data model layers
• Operation and function are used here interchangeably but the term Geoprocessing will be used for spatial analysis technique concepts and description in this module

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Common Basic Analysis Techniques

• Query
• Selection
• Classification
• Buffer
• Clip
• Intersect
• Merge
• Union
• Dissolve
• Overlay (vector and raster)

Caution: Different software packages may use different terms for these analysis techniques

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Module 7.1 and 7.2 will focus on tools and techniques from ArcGIS Pro

Spatial Operations or Functions - Geoprocessing

There are hundreds of operations or functions available for use in spatial analysis and this Module 7.1 will be limited to common or basic geoprocessing functions and operations

Module 7.2 will introduce additional spatial analysis techniques including briefly covering data models, modeling and programming

Modules in Unit 8 will include analysis processes for remote sensing imagery data

Bolstad, Fig. 9-1

Simple Analysis – Comparison Using Feature Attributes

• Use a Feature data layer of US States having attributes about each State’s population
• Make comparison by using Symbology tools based on an attribute
• Symbolize into a number of classes (values) using the Field for population per square mile

Simple Question – Compare Population Density � By State Area (per square mile) Using Symbology

Changing Symbology – to Unique Values

• Unique Values were specified for the 9 Classes for comparison across the USA
• Emphasis was added by indually changing the colors for the highest classes
• Zooming in allows comparison of classes in California and Nevada
• Zooming in more you can see population classes in San Francisco region

Selection Operations

• A selection operation identifies features based upon one or several criteria such as the previous example of the query to display a comparison of population density by States using a color ramp or into unique values by Population Class
• Selection operations can also be performed using set algebra or Boolean operators

Set Algebra

• Set algebra uses greater than, less than, equals to or not equal to ( <, >, = or <> ) to define an output

Software Selections can include:

• Select All States = entirely north of Arkansas
• Select All Features Where State Areas > 84,000mi²

Combined Selection:

• Select all Features where States = north of Arkansas And Area > 84,000mi²

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Bolstad Fig. 9-3

Selection by Attribute

Boolean Algebra

• Boolean algebra uses conditions of AND, OR or NOT

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Bolstad, Fig. 9-5

Boolean Logic

Bolstad, Fig. 9-6

Spatial Selection – Select by Location

• Select by Location operations selects a set of features from an Input Feature Layer where features in the Selecting Feature layer satisfies the specified relationship parameter, such as
• Boundary touches: Features that touch other features
• Contains: Features that contain or are within other features
• Intersect: Features that the feature
• Within a distance:
• . . . . . .

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Adjacency - Select by Location

• What if you want to identify all States that share a boundary with Idaho?
• You can do a Select by Location to find those States
• You can then create a new data set including those states

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Containment - Contain

• What states contain the Mississippi River?

Esri Spatial Selections

• Intersect
• Are within the distance of
• Are within
• Are completely within
• Contain
• Have their centroid in
• Share a line segment with
• Touch the boundary of
• Are identical to
• Are crossed by the outline of

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(From Esri Help Using Select by Location)

Classification

• Classification
• A spatial data operation that is often used in conjunction with selection
• A classification, also known as reclassification or recoding, will categorize geographic objects based on a set of conditions

Bolstad Fig. 9-13

Classification – Comparison of Vacancies By State

• To classify ranges of values, a histogram can be used
• Based upon the histogram and map purpose, various classification methods can be selected

Selecting a Classification Method

• Each of these maps was produced with the same data
• Which one best represents the population distribution?
• Careful observation of the histogram is required before choosing a classification method

Equal Interval

Equal Area

Natural Breaks

Other Classification Methods

• Quantile
• Classified so that there are an equal number of features in each class
• Standard Deviation
• Classified by the number of standard deviations from the average. Only appropriate for normal distributions
• Maximum Breaks
• Class breaks are determined by the largest gaps in the data when ordered from low to high

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Merge and Dissolve Functions

• A dissolve operation combines similar features into one feature
• The example to the left shows a dissolve operation to create a region containing the States bordering the Mississippi River

Visualizing Outcomes

• For clarity, some examples in this section are in black and white
• Visualization of outcomes from spatial analysis should use appropriate cartographic design
• Focused on the needs of the audience
• Module 7.2 continues exploring spatial analysis functions and concepts and briefly introduces programming (coding)

See GeoTech Center website (https://geotechcenter.org) �for additional Model Courses and other curriculum resources. ���������Note: some content is a derivative of other authors���

Ann Johnson

Associate Director

ann@baremt.com

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2-17-2021 V7