Vector GIS GeoDatabases

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Vector GIS -- GeoDatabases
GeoDatabases Defined
A GeoDatabase is a generic model of geographic
information, consisting of topologically
integrated feature classes, roughly similar to
the ArcInfo coverage model The coverage model
is extended to support complex networks
connectivity topological rules can be specified
and to facilitate relationships between and among
feature classes shared and linked feature
geometry can also be specified
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Vector GIS Implementing GeoDatabases
GeoDatabases Implemented
GeoDatabases are implemented on any standard
Relational Database Management System using the
ArcSDE server ArcSDE defines an open interface
between ArcGIS and the RDBMS application,
allowing ArcGIS to manage the spatial data using
ORACLE, MS SQL Server, IBM DB2, INFORMIX,
etc. For small single-user applications, you can
design and implement a personal GeoDatabase that
is managed by the MS Access JET Engine without
the necessity of ArcSDE
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Vector GIS GeoDatabase Model Features
GeoDatabase Model Design

• Supports an object-oriented vector spatial data
  model
• All entities, including spatial features are
  represented as objects, which are instances of
  object classes
• All objects have
• Properties name, length, etc.
• Behaviors can be modified, can have
  descriptive attribute collections
• Relationships when a node is moved, an arc
  end-point also moves with it
• Object types include
• Simple objects objects without locations
• Geographic features objects with locations
• Network features objects that are
  geometrically integrated with other features,
  such as nodes and arcs
• Annotation features text or graphic objects
  with location
• You can define relationships between objects
  and specify rules for maintaining referential
  integrity among the objects

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Vector GIS GeoDatabase Objects and Classes
Objects and Object Classes

• Object Classes are generic objects that
  encapsulate a set of properties and behaviors
  for all instances of that object
• Objects are instantiations of those parent
  object classes that share all the properties and
  behaviors of the object class
• e.g. An Automobile is an object class, with
  the properties Manufacture, Model, and Color,
  and the behaviors Accelerate and Decelerate. A
  red Gull-wing 2000 Ferrari that can reach 60
  mph in 4 seconds and can stop as quickly is an
  object!
• In the context of ArcGIS, object classes are of
  two general types
• Spatial Feature Class polygon or Non-spatial
  Object Class table
• Every object class has a unique Identifier
  property OID that is unique for every
  instantiation of the class
• All objects of a class must have the same
  properties defined in the class, but the object
  classes may have sub-types
• Sub-types hold default values for class
  properties color is a class property, w/
  monochromatic, bichromatic and poly-chromatic
  sub-types
• Domains can be set for each sub-type the
  monochromatic sub-type may be restricted to only
  either Red or Yellow color domains

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Vector GIS Database Schema
GeoDatabase Schema

• The GeoDatabase Schema is defined as the
  structure of a database or a database object
  table, including all properties, behaviors and
  relationships
• The first step in designing the GeoDatabase is
  designing its schema
• Questions that lend themselves to schema design
  include
• What kind of data will be stored in the
  database?
• What projection / coordinate system will the
  datasets have?
• What rules will you have for modifying spatial
  features?
• What object classes will you have in your
  database?
• Will the object classes have sub-types?
• If there are sub-types, will there be
  associated domains?
• Will there be relationships between different
  objects?
• If there are shared geometric relationships
  between feature object classes, will you set up
  rules for modifying features?

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Vector GIS Creating GeoDatabases I
Steps in GeoDatabase Model Design

• Design the Schema of the GeoDatabase
• Create the geoDatabase and name it
• Create feature groups or features or objects
  from scratch
• or
• Import or migrate existing feature groups and
  features from shapefiles, coverages, tables,
  annotations, etc
• Define sub-types for all necessary classes
• Define attribute domains for sub-types as
  needed
• Define relationships between object classes
  sharing geometry between and among features, or
  relationships between a feature table and an
  attribute table
• Define network rules for topology, if any

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Vector GIS GeoDatabase Object Class Typology
Non-spatial Object Class
Spatial Object Class
Simple Feature Class
Integrated Feature Class
Node Feature Dataset Arc Feature Dataset Poly
Feature Dataset
Polygon Feature Dataset
Table
Sub-types
Sub-types
Sub-types
Spatial Domains Attribute Domains
Spatial Domains Attribute Domains
Attribute Domains
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Vector GIS GeoDatabase Relationship Classes

• Relationships between objects are defined and
  named
• Relationships are stored in a special
  Relationship Class
• The Relationship Class contains the particulars
  of the relationships between object classes
  e.g. Cardinality Ratio
• In the example below, note that an owner can
  own more than one parcel
• The relationship therefore has to be specified
  between a non- spatial class Table and a
  spatial feature class Polygon feature dataset

M
1
M
1
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Vector GIS GeoDatabase Relationship Classes
Implemented

• Parcel Number in the Parcel Polygon Feature
  spatial Table Class is a foreign key in the
  Owners Class non-spatial
• Referential Integrity can thus be enforced
• If Donald Trump buys out John Smythe, John
  Smythe disappears from the Owners Class, but
  nothing happens to the feature class
• If Parcels 0017 and 0018 are combined into a
  new feature Parcel 0018, then referential
  integrity constraints force the removal of John
  Smythe from the Owners Class

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Vector GIS -- Editing Features on a Single Theme
Single Theme Spatial Editing Operations include

• Creating new features and adding relevant
  attributes
• Spatially editing/modifying existing features
• copying, moving, extending, trimming features
• resizing, buffering or mirroring features
• adding, deleting, moving vertices of features
• Setting snap options
• Appending adjacent polygons
• Splitting line or polygon features using lines
• Unioning or Merging features
• Intersecting features
• Creating/editing attributes of modified features

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Vector GIS Setting Snap Options during Editing
Setting SNAP Options
Whenever you make spatial edits to a theme, like
adding features or modifying features, you
cannot rely on visual judgment -- at a different
scale, a polygon feature might appear to be a
point! What you need to do is to set snap
options, so that every editing mouse click
jumps to the nearest vertex within a specified
distance, thereby eliminating judgment If no
vertex is found within the specified snap
distance, the point is placed at the location
specified by the mouse-click
Mouse-click at center of cross-hairs Actual point
jumps to vertex P
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Vector GIS Setting Snap Tolerance
Setting SNAP Options -- Tolerance

• Setting Snap Tolerance
• Snap Tolerance is the distance within which
  automatic snapping occurs to another feature or
  sub-feature objects location
• The circle around the pointer represents the
  snapping tolerance
• If the location being snapped to is outside the
  snapping tolerance, the snapping location stays
  with the pointer
• If the location being snapped to is inside the
  snapping tolerance, the snapping location moves
  away from the pointer and snaps to the target
  location

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Vector GIS Setting Snap Properties
Setting SNAP Options -- Properties

• Setting Snap Properties
• You can choose any or all of the parts of
  existing features -- vertex, edge, or endpoint
  -- to which you want your new feature to snap by
  setting the layer snapping properties
• When the pointer comes within the snapping
  tolerance of the vertex/edge/endpoint of an
  existing feature, the vertex of the new feature
  where you click snaps to the vertex/edge/endpoi
  nt of the existing feature
• If the pointer click event occurs outside the
  snapping tolerance of any vertex/edge/endpoint
  of an existing feature, the vertex of the new
  feature is created at the location of the click
  event

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Vector GIS Setting Snap Priorities
Setting SNAP Options -- Priorities

• Setting Snap Layer Priorities
• You can also set the snapping priority for
  layers on your map
• The order of layers listed in the Snapping
  Environment options dialog determines the order
  in which snapping will occur
• Snapping occurs first in the layer at the top
  of the list and then in each consecutive layer
  down the list
• You can easily change the snapping priority by
  dragging the layer names to new locations within
  the layer list

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Editing Vertices of Vector Features
Feature Vertex Editing

• In many instances, line or polygon shapes may
  have to be altered
• The shapes of the features are edited
  individually, by adding, deleting or moving
  vertices

moving vertices
adding vertices
deleting vertices
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Maintaining Topological Integrity during Polygon
Editing
Maintaining Adjacency while adding polygons

• Whenever polygons have to be added to an
  existing data set of polygons, adjacency rules
  must not be violated
• While the GIS permits polygon features to
  overlap (violating adjacency rules), area
  calculations and overlay operations will lead to
  erroneous results
• The overlapping regions must be cleaned
  and the topology rebuilt for the new, clean
  theme, which may have sliver polygons
• Instead of this process, if a little care is
  taken during the process of adding polygons,
  adjacency rules need not be violated, and
  topology is built on the fly for the new
  feature only

sliver polygon
Adjacency Rules Violated
Adjacency Rules Preserved
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Splitting Polygon or Line Features Using Lines
Splitting Lines or Polygons using Lines

• Line or Polygon features may be split using
  graphic line objects, with input features
  being deleted from the database
• Before splitting, rules must be established
  for the transfer of attributes from the original
  features to the new features
• Numeric attributes can be transferred in the
  same ratio as output_feature_area to
  input_feature_area, relying on the assumption
  that the numeric attributes are distributed
  uniformly throughout the extents of the input
  feature only for GeoDatabases
• String attributes are either copied or left
  blank in the output features

ID - Poly_A Area - 58 Pop - 290
INPUT
OUTPUT
splitter
ID - Poly_A Area - 42 Pop - 210
Input_feature_ID - Poly_A Input_feature_Area - 1
00 Input_feature_Pop - 500
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Merging features in a theme
Merging Features in a single Theme

• The merge process combines several input
  features into one output feature on the same
  theme -- the input features are deleted from the
  database
• As in the split feature case, rules must be
  established for the transfer of attributes from
  the input features to the output features
• Numeric attributes can be aggregated from
  the input features and transferred to the result
  feature
• String attributes are either copied or left
  blank

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INPUT
OUTPUT
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Unioning features in a theme
Unioning Features in a single Theme

• The Union process is very similar to the Merge
  process it combines several input features
  into one output feature on the same theme -- the
  input features are not deleted from the database
  -- a new feature is created and the old input
  features remain in the dataset

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INPUT
OUTPUT
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Intersecting Features in a theme
Intersecting Features in a single Theme
The intersect process computes the geometric
intersection of selected input features and
produces new features without deleting the input
features
Note polygons in red will be not be deleted --
the red polygons are just shown for reference.
The blue polygon is the new resulting feature
INPUT
OUTPUT