Spatial Analysis –
vector data analysis
Lecture 2
Recap: three data models
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Vector
Raster
Geodatabase (object-oriented data model)
• Vector data and table
• feature class is the basis
• Raster data
The real world is complex. Neither discrete (object) nor continuous
(field) can perfectly represent some of real world situations. We need
combined model: dual, hybrid, or object-oriented approach
Spatial Analysis tools in
ArcToolBox
Vector data analysis:
Shapefile &
Feature class/table
Raster data analysis
Details
Vector
1. Extract
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To create a new subset from the input
(shapefile, features and attributes in a
feature class or table) based on spatial
intersection or an attribute query.
• Clip
• Select
• Split
• Table select
Clip
XY tolerance:
The minimum distance
separating all feature
coordinates (nodes and
vertices) as well as the
distance a coordinate can
move in X or Y (or both). You
can set the value to be higher
for data that has less
coordinate accuracy and
lower for datasets with
extremely high accuracy.
Learn
more
from
help
Select
Split
Table select
2. Overlay
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Joining two existing sets of features into a
single set of features to identify spatial
relationships between the input features.
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Erase
Identify
Intersect
Spatial Join
Symmetrical difference
Union
Update
3. Proximity
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Identify features that are closest to one
another, calculate the distances around them,
and calculate distances between them.
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Buffer
Create Thiessen Polygon
Generate Near Table
Multiple ring buffer
Near
Point distance
Not dissolved
Dissolved
Example
How to form Thiessen polygons
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Also known as 'Voronoi networks' and
'Delaunay triangulations', Thiessen
polygons were independently discovered in
several fields of study, including climatology
and geography. They are named after a
climatologist who used them to perform a
transformation from point climate stations to
watersheds.
Thiessen polygons can be used to describe
the area of influence of a point in a set of
points. If you take a set of points and
connect each point to its nearest neighbor,
you have what's called a triangulated
irregular network (TIN). If you bisect each
connecting line segment perpendicularly
and create closed polygons with the
perpendicular bisectors, the result will be a
set of Thiessen polygons. The area
contained in each polygon is closer to the
point on which the polygon is based than to
any other point in the dataset.
Statistics
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Basic statistic to the attribute table
• Frequency
• Summary statistics