Vector Analysis Methods

Querying and overlaying vector layers, key operations and techniques.

Vector Analysis Methods

Many operations can be done with vector data.

Some methods are very similar.
- Distinctions between methods can be subtle, but important.
- Can complete the same tasks, but need slight changes to a workflow.
Typically in GIS there are multiple ways to get the same answers.
- Some “routes” are just more direct.

Querying Attributes

Finding features of interest based on attributes.

A good way to reduce data volumes, export queries to new layers
In ArcGIS Pro you can Select by Attribute
- Uses SQL (Structured Query Language)
- Check equality, relative magnitude, etc.
- Combined with operators: AND / OR

Querying Attributes

Finding features of interest based on attributes.

If we’re only interested in historic residential buildings:
- Where “YEAR BUILT” ≤ 1950 AND
  “TYPE” = “Residential”
- Save as a new layer, won’t have to search through all the objects every time.

Select by Attribute

Sample SQL queries

Where “SPECIES” = “Pine”
Where “SPECIES” ≠ “Pine”
Where “HEIGHT” ≤ 5
Where “SPECIES” = “Pine” AND “HEIGHT” ≤ 5
Where “SPECIES” = “Pine” fc0314OR “HEIGHT” ≤ 5

Species	Age	Height
Pine	10	5
Pine	95	28
Oak	200	25
Oak	5	4

Select by Attribute

Sample SQL queries

Where “SPECIES” = “Pine”
Where “SPECIES” ≠ “Pine”
Where “HEIGHT” ≤ 5
Where “SPECIES” = “Pine” AND “HEIGHT” ≤ 5
Where “SPECIES” = “Pine” OR “HEIGHT” ≤ 5

Species	Age	Height
Pine	10	5
Pine	95	28
Oak	200	25
Oak	5	4

Select by Attribute

Sample SQL queries

Where “SPECIES” = “Pine”
Where “SPECIES” ≠ “Pine”
Where “HEIGHT” ≤ 5
Where “SPECIES” = “Pine” AND “HEIGHT” ≤ 5
Where “SPECIES” = “Pine” OR “HEIGHT” ≤ 5

Species	Age	Height
Pine	10	5
Pine	95	28
Oak	200	25
Oak	5	4

Select by Attribute

Sample SQL queries

Where “SPECIES” = “Pine”
Where “SPECIES” ≠ “Pine”
Where “HEIGHT” ≤ 5
Where “SPECIES” = “Pine” AND “HEIGHT” ≤ 5
Where “SPECIES” = “Pine” OR “HEIGHT” ≤ 5

Species	Age	Height
Pine	10	5
Pine	95	28
Oak	200	25
Oak	5	4

Select by Attribute

Sample SQL queries

Where “SPECIES” = “Pine”
Where “SPECIES” ≠ “Pine”
Where “HEIGHT” ≤ 5
Where “SPECIES” = “Pine” AND “HEIGHT” ≤ 5
Where “SPECIES” = “Pine” OR “HEIGHT” ≤ 5

Species	Age	Height
Pine	10	5
Pine	95	28
Oak	200	25
Oak	5	4

TopHat Question 1

How many rows in this table would the following query return?

Where “SPECIES” = “Pine” AND “SPECIES” = “Oak”

Species	Age	Height
Pine	10	5
Pine	95	28
Oak	200	25
Oak	5	4
Birch	5	4

TopHat Question 2

How many rows in this table would the following query return?

Where “SPECIES” = “Pine” OR “SPECIES” = “Oak”

Species	Age	Height
Pine	10	5
Pine	95	28
Oak	200	25
Oak	5	4
Birch	5	4

Proximity Analysis

Looking at spatial relationships within or between layers.

A good way to reduce data volumes, export queries to new layers.
Multiple options, depending on our needs.
If we’re only interested in buildings within 1 km of streams:
- Identify by proximity
- Save as a new layer, won’t have to search through all the objects every time.

Select by Location

Use to check for spatial relationships such as:

Containment
Intersection
Distance

Geometric Manipulations

These methods create new layers with altered “geometries”. Geometry is a term we use to refer to points, lines, and/or polygons in a vector layer.

Buffer

Create a new Polygon layer based on distance.

Buffer points, lines, or polygons using a buffer distance or set a field to specify varriable distance.
Use the Multiple Ring Buffer tool for multi-criteria buffers.

Example From ESRI Docs

Buffer

Create a new Polygon layer based on distance.

Buffer points, lines, or polygons using a buffer distance or set a field to specify varriable distance.
Use the Multiple Ring Buffer tool for multi-criteria buffers.

Buffering Tsunami Shelters

Dissolve

Aggregates features.

Merges objects completely or by attribute(s).
Can calculate statistics for aggregated regions.
Useful if our data is more “complex” than we need it to be.

Example From ESRI Docs

Dissolve

Aggregates features.

Merges objects completely or by attribute(s).
Can calculate statistics for aggregated regions.
Useful if our data is more “complex” than we need it to be.

Dissolve Shelter Buffers

TopHat Question 3

This tool allows us to aggregate vector objects in a layer, either completely or by specific attribute values.

Buffer
Dissolve
Select by Attribute
Merge

Feature Overlay

When we have multiple data layers and we want to combine them to form a new output.

Clip

Cut one layer down to the boundaries of another.

Useful when we want to focus on a study area
Does not alter attributes
- Input layer: our data layer
- Clip layer: the study area

Example From ESRI Docs

Clip

Cut one layer down to the boundaries of another.

Useful when we want to focus on a study area
Does not alter attributes
- Input layer: our data layer
- Clip layer: the study area

Input

Clip

Cut one layer down to the boundaries of another.

Useful when we want to focus on a study area
Does not alter attributes
- Input layer: our data layer
- Clip layer: the study area

Output

Erase

Remove the area of one layer from another.

Opposite of the clip tool
Does not alter attributes
Useful when we want to discard/exclude an area

Example From ESRI Docs

Erase

Remove the area of one layer from another.

Opposite of the clip tool
Does not alter attributes
Useful when we want to discard/exclude an area

Input

Erase

Remove the area of one layer from another.

Opposite of the clip tool
Does not alter attributes
Useful when we want to discard/exclude an area

Output

Intersect

Output where layers overlap and combine attributes.

Can handle more than two layers at once
Splits features by overlaps and merges attribute tables
Merge and parse data at the same time

Example From ESRI Docs

Intersect

Output where layers overlap and combine attributes.

Can handle more than two layers at once
Splits features by overlaps and merges attribute tables
Merge and parse data at the same time

Input

Intersect

Output where layers overlap and combine attributes.

Can handle more than two layers at once
Splits features by overlaps and merges attribute tables
Merge and parse data at the same time

Output

Union

Combine multiple polygon layers, split features where they overlap and combine attributes.

Similar to intersect, but keeps overlapping areas
Adds attributes from all overlaps.
Can handle more than two layers at once.
- Null values where for new attributes where no overlaps are present.

Union

Combine multiple polygon layers, split features where they overlap and combine attributes.

Similar to intersect, but keeps overlapping areas

Many More

There are many more vector overlay tools! I have presented some of the the most frequently used tools, but if you have specific use cases you may need others. I can’t cover them all, and I don’t want to overwhelm folks.

TopHat Question 4

Clip and erase remove portions of layer based on location relative to another layer but they do not alter the attribute table.

True
False

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Vector Analysis Methods Querying and overlaying vector layers, key operations and techniques.

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