Vector Analysis

Vector Analysis
- Spatial Analysis
  - Spatial Calculation
    - straight-line distance (use "ruler")
    - feature size
      - calculation in data table
      - may need to recalculate
      - e.g.: length, perimeter, area
  - Select by Location
    - feature selected based on SPATIAL relation to other features
    - compare two themes
      - features selected from TARGET layer ...
      - ... based on features in SOURCE layer
    - examples
      - intersect
        
        share a common point:
        
        road segments intersecting streams = crossings
        
        road segments intersecting fault lines
      - contain
        
        features within other features:
        
        stands containing wildlife trees
        
        lakes containing islands
      - within a distance of
        
        "within a buffer":
        
        CMT's within 50m of new road
        
        properties within 1km of schools
      - many others!!
  - Buffer
    - 3 types:
    - can buffer both outside (typical) or inside of polygons
    - option to dissolve overlapping buffers
  - Overlay
    - combine two data layers (themes)
    - types of overlays
      - Clip [Extract]
        
        area defined by 'clip overlay theme' (= cookie cutter = "mini me")
        
        table contains only fields from input theme NOT clip theme
        
        e.g. future cutblock & forest inventory
      - Intersect
        
        area is where they overlap (= coincident = AND)
        
        table contains all fields from both themes
        
        e.g. landowners & forest
      - Union
        
        area is the total area of both (= combined area = OR)
        
        table contains all fields from both themes
        
        e.g. fine text. soils & steep slopes
      - Update
        
        updates features - 'overlay & replace'
        
        fields in both layers have to match
        
        e.g. fire/ logging on top of inventory
      - Erase
        
        'overlay & eliminate'
        
        fields from 'erase layer' not used
        
        e.g. expropriate parkland from timberland
  - Data Mgmt
    - General
      - Merge
        
        combines 2+ layers and makes a new 'combined layer'
        
        e.g. combine all the buffers
      - Append
        
        combines 2+ layers into an existing layer
        
        e.g. add new cutblocks (CP 22) into existing
    - Generalization
      - creates a new "simplified" data layer
      - Dissolve
        
        creates a new data layer
        
        merge adjacent polygons based on common attribute
        
        e.g. merge stand types that are old growth
        
        new theme is a simplified (generalized) version of the original
      - Aggregate
        
        ploygons within certain distance of each other
      - Smooth
        
        more visually pleasing output
      - Simplify
        
        removes small fluctuations in lines
  - Satial Join
    - database join: "key fields" (primary & secondary)
    - spatial join: coincident space (determines what records 'are attached' to each map feature)
    - e.g. bear dens <-- forest polygons
      - forest stand info is added to the bear den table
      - in DB talk we say ... destination <-- source
      - in spatial join we say ... target features <-- join features
  - Network Analysis
    - analyze movement through a network (e.g. road network)
    - analyses
      - point-to-point: shortest path vs quickest path
      - efficient routing
      - location-allocation
    - factors
      - length of segment
      - impedence on flow
      - impedence on turns
- Attribute Analysis
  - Select by Attribute
    - simple query has 3 parts
      - field name
      - operator (relational)
      - value
    - complex query
      - >1 simple query
      - combined with Boolean operators
        
        AND
        
        OR
        
        NOT
  - Relating Tables
    - 'attaches' outside data "to the map" (i.e. its data table)
    - join
      - one-one
      - many-one
    - link
      - one-many
  - Arithmetic Calculation
    - apply formula to a numeric field
    - + - / *, powers, trig, etc.
  - Statistics
    - sum, mean, min, max, std dev, histogram
    - ArcGIS: 'Statistics'
      - pop-up table
      - temporary
    - ArcGIS: 'Summarize'
      - you set which stats are generated
      - creates a data table
  - (Re)classification
    - Generalization / simplification of data
    - done via Symbology
    - temporary (vs Dissolve which is perm.)
    - schemes
      - natural break
      - quantile
      - equal interval
      - user defined
      - std deviation