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Lecture 8 Chapter 10

Terms in this set (14)

If spatial joins are not good to use in a specific situation because the features don't always fall neatly inside another, what tool can you use instead?
What does that tool do?
You can use the tool OVERLAY when the spatial join isn't good!
Overlay provides a way to split features so that there is always a one to one correspondence
What are the negatives of using a spatial join?
1) Not all features fall neatly inside another
2) Cannot work with categorical data
What are the two types of overlay?
Extraction function
Overlay with attributes
Describe the two types of overlay
Extraction function:
- Combine the features but do not combine the tables
- use click and erase

Overlay with attributes:
- Combine the features AND the tables
- use intersect and union
How is extraction functions not similar to select by location ?
They are similar, but the only difference is that extraction function can split features that cross the boundaries.
What's the negative thing about using clip/erase?
that they can change the length or areas of features on the boundaries so you need to update them.
Geodatabase shape_area and shape_length field are automatically updated but other field such as JUST area or lengths are not..

Shape files do NOT update any area of length field automatically so you gotta recalculate them!
Overlay with attributes (3)
1) Joins features based on common location
2) Forces features to split when they overlap each other, creating new features
3) Enforces one-to-one cardinality between features in order to join attributes
For points and polygons...
Overlay does the same things as spatial joins
Dissolve
- Eliminate all the attributes in the table except the dissolved one
- Group features together based on whether they share the same value of an attribute field
- output: single feature or multiple feature
Buffer
It is used to identify areas that fall within a certain distance of a set of features. Buffers can be created for points, lines or polygons.
What are slivers?
There are tiny polygons created during geoprocessing, that result of slight differences in boundaries.
What's GEOPROCESSING?
- Execute analysis functions and tools
- Stringing together analysis functions to achieve a result
Where do you save your current and scratch workspace?
Environment->workspace
Model Builders
It is where you can create models built from sequences of tools.
You can store these models and use them for later reference. You can use them with different inputs.
And you can share the models with others!
You can then transfer them to be SCRIPTS! where you can modify the model and put replay if you want to.
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