lecture 6

1. boolean operations

operators: true or false(0 or 1)

resulting from: union(logical or ) ∨

intersection(logical and)

negation(logical not)

elclusion(XOR) of 2 or more sets   a、b两个值不相同，则异或结果为1。如果a、b两个值相同，异或结果为0

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2. buffering

buffering is a process that creates an area (polygon) around a feature, the result is a new polygon layer

3. erasing

or deleting data from a layer to create a new layer can  be implemented in one of two main ways

4. extracting

reverse with erasing, maintaing only specidied areas

5. merging

removing unnecessary or superfluous polygon boundaries

6. updating

creates a new layer based on data in an existing layer by updating, or altering, a portion of the data(spatial or attribute) based on another, independent layer

7. vector overlay

combining two paper maps into one new paper map