1047955205__proximity analysis

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1047955205__proximity analysis Powered By Docstoc
					Tracy K. Holloman
    EVSC 468
 March 18, 2003
                     Topics
   What is Proximity?
   Tools
   Select By Location Description
   Buffer Wizard Description
   Advantages of Different Methodologies
   Capabilities
   Sensitivity Analysis
   Conclusions
   Demonstration
    What is Proximity????
                CLOSENESS
 Within the vicinity of a certain feature or
                    landmark
   Importance: Essential to determining
 whether a certain feature will impede your
    ability to travel to a specified location
  Best route and location determination
Tools For Determining
      Closeness
      Select By Location
        Buffer Wizard
        Select By Location
 Uses Standard Query Language to
  describe an association between two Layers
 Selects a set of features that fall within a
  specified distance of the pre-determined
  feature class
 Results = Highlights selected features, does
  not degrade the integrity of the original data
  in any way
Select by Location




    PROCEDURE
       STEP 1:
  Choose selection:
        Select
        Add to
       Remove
Or Select from current
Selection (second level
     of selection)
         Step 2:
   Choose the layer
   you would like to
  select features from,
 add to, remove from,
or select from currently
    selected features
           Step 3:
  Choose the Relationship
  Between your two layers:
          Intersect
  Are Within a Distance of
   Are Completely Within
    Completely Contain
    Have Their Center in
 Share a Line Segment With
   Touch the Boundary of
      Are Identical to
Are Crossed by the Outline of
          Contain
     Are Contained By
          Step 4:
   Choose the Second
layer that you would like
to use in conjunction with
     your initial layer
       Step 5:
Choose the distance
and units you would
 like your buffer to
       include
Step 6: Apply!!




Results = Teal
              What is a Buffer?
 An object created that embodies components of
  existing objects
 Works well with impact analysis
 Both raster and vector data sets can use buffering
  capabilities
 3 types: causative (extent of toxic spill), mandatory
  (deals with either land use or zoning), arbitrary (used in
    conjunction with sensitivity analysis)
Buffer Wizard




 PROCEDURE
     Step 1:
 Select the layer
you would like to
apply the buffer to
     Step 2:
    Implement
the distance your
    buffer will
     embody
      Step 3:
     Choose the
  name you would
like for your output
     Shapefile

       NOTE:
 You can choose to
  dissolve barriers
  or leave them as
       a means
 of distinguishing
     individual
    components
Step 4: Hit Finish




   Buffers = Brown!!
Advantages/Disadvantages of
    Each Methodology
 Select by Location does not disrupt the
  original data, it simply selects the features
  meeting a certain standard and highlights
  them
 Buffer Wizard allows creation of a new
  layer which can be edited—not simply a
  graphic display
    What can these tools do??
 Accessibility: the size and closeness of a given
  activity system with respect to a certain zone
 Choice: allows routes to be chosen on basis of
  connectivity and integration
 Safety and Security: enables one to determine
  the area affected by pollution or a spill situation
 System management: determine routing to
  insure efficiency and maintenance of population
  needs
                 Analysis
 To demonstrate the functions available
  through GIS, I downloaded several
  shapefiles containing roads, railways,
  landmarks and hydro features within
  Chesterfield County Virginia
 Lets determine the railways that lie within a
  1 mile distance of landmarks
               Methodology
 Add both the rail and landmark layer to the
  ArcMap Data Frame
 Choose the Select by Location menu
 Select Features from the Rail Layer that are
  within a distance of 1 mile of the landmark
  layer
 Hit apply
Methodology Continued
 Once the select by location has
  been applied selected features will
  be highlighted in teal
 To see the actual features that were
  highlighted right click on the Rail Layer
 Open the Attribute Table
 Hit Selected Features to obtain a complete
  listing of the selected features
Road Placement with Respect
       to Landmarks
   Next, I would like to examine how Buffer Wizard
    could be used to examine Road placement with
    regard to Landmarks
   Add both the Landmarks and road layers to the
    Data Frame
   To begin with I selected Buffer Wizard
   I would like to buffer features within the
    Landmark Layer
   I wanted a .25 mile buffer around this layer to
    determine roads within close proximity
Note: Buffered areas appear brown by default
      Hydrology within .5 mi. of
             roadways
   How could stream networks influence roadways?
   Could flooding plague certain areas?
   Add both the hydro and road layers
   Choose Select by location
   Select features from the Hydro Layer that are
    within a distance of .5 mi. of the Roads Layer
   Features Selected are highlighted in teal
Note: numerous hydrological features are within .5 mi of roadways
      Sensitivity analysis
 Perhaps by manipulating the distance
  between the hydro layer and the road layer
  we can get a better feel for their relationship
 Choose three distances, say .25, .5 and .75
  miles
 Determine the number of hydro features
  embodied by each to see if parameter
  variation is in fact important
1386 Out of 1562 hydro features are highlighted when the buffer is
                            .25 mi.
Note: 1482 out of 1562 hydro features highlighted when buffer
                          Is .5 mi.
Note: 1516 out of 1562 features in hydro layer selected when
                 .75 mi. buffer is employed
                  Variation
 Inconsistencies: data exploration to determine
  “key” sensitive parameter = necessary
 Consistency: robust data
 Therefore, the further away from the hydro layer
  you go the more roads are encapsulated
 Thus, determination of the exact flooding extent
  certain frequency storms could induce should be
  determined to quantify the precise number of
  roadways affected
             Conclusions
 Select by Location and Buffer Wizard are
  vital components of proximity analysis
 Both can give you graphical output,
  however, buffer wizard enables the creation
  of new shapefiles based on results
 Sensitivity analysis is key to determining
  the extent to which parameters affect the
  overall outcome of analysis
         Demonstration
   Roads within a .25 mile distance of
               landmarks:
       A--using select by location
         B--using buffer wizard
Questions

				
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