GTECH 361
Lecture 10
Behavior and the Geodatabase
Rules and Behavior
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..is what makes geodatabase features
smart
Enforcing integrity with attribute
domains
Grouping features using subtypes
Table relationships
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Between feature classes
Between feature classes and non-spatial
tables
Attribute Domains
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Define what values are allowed for a
field in a feature or a non-spatial table
Created and edited in ArcCatalog
Attribute Domains
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Are a specialization of well-known data types
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ValveTypeDomain is a Long Integer with a
permissible value range from 1..10
Enforcing Data Integrity
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Preventing errors during data entry
Checking validity after the fact
Types of Attribute Domains
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Range domains
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Coded value domains
Split and Merge Policies
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Use attribute domains to specify how
attributes are handled after the split or
merge
Manage attributes that will be affected
by edits to a feature's geometry
Split Policies
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Duplicate
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Default value
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Geometry ratio
Merge Policies
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Default value
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Sum
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Weighted average
Field Type Limitations
to Split and Merge Policies
Merge
Policy
Options
Field
Types
Split Policy
Options
Coded
Value
Domain
Date, double,
float, long
integer, short
integer, text
Default value,
Duplicate
Default value
Range
Domain
Date, double,
float, long
integer, short
integer
Default value,
Duplicate,
Geometry
ratio
Default value,
Sum values,
Weighted
average
Subtypes
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The closest we get to object-orientation
in the geodatabase
To group similar features without
creating a new feature class
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Group parcels into residential, commercial,
and agricultural subtypes and associate
different attribute domains with each group
Faster than many feature classes
Subtypes in ArcGIS Versions
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ArcView
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Only displays subtypes
ArcEditor, ArcInfo
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Create, edit and use subtypes
Example of a Subtype
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Subtypes of feature class country_lanes
Example of a Subtype
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Subtype encoding and decoding
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Feature class table
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ArcMap
Table of
Contents
Creating a Subtype
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Based on an existing attribute, or
A new field containing subtype values
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Values have to be short or long integer
For each subtype, you can associate
default field values and domains
You have to define one default type
Once defined the new subtype can
become target of an ArcMap edit
operation
Using Subtypes with Features
Everything is Related…
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to everything else but… (Tobler’s Law)
This multitude of relationships is usually
not well captured in a GIS database
Which makes tracking real-world
situations difficult
For instance…
Cardinality
Relationships Across Tables
Relationship Definitions
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Require primary and foreign key to be
of the same type
Supported field types are
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short integer
long integer
float
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double
text
object ID
Relationship Classes
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Permanently stored in the geodatabase
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Hence different from joins and relates in
ArcMap, which are only stored in .mxd
Within but not across geodatabase(s)
Once created cannot be modified
If corresponding table is deleted, the
relationship class is deleted automatically
Only 2 tables can be related per R.C.
Relationship Properties
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Cardinality, origin and destination tables
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As discussed before
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Labels
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Relationship types and messaging
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Attributes
Relationship Labels
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Relationship classes have forward and
backward path labels
Relationship Types
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Simple
Table objects exist independently of
each other
Composite
Destination objects cannot exist without
an origin object
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Forward messaging only
One-to-one or one-to-many cardinality
Relationship Attributes
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Relationship classes can have attributes
describing the relationship
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E.g, in a relationship between parcels and
owners, an attribute of the relationship
may be the percentage of ownership
Relationship Classes,
Relates and Joins
Relationship
Class
Relate
Join
Typical Uses Modeling and editing Querying, Querying, labeling,
related objects
selecting
symbolizing
Referential
Integrity
Yes
No
No
Messaging
Yes
No
No
Attributes
Yes
No
No
Relationship Yes
Rules
No
No
Cardinality
All
One-to-one, manyto-one
All
Relationship Rules
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Control how records in the origin and
destination tables can be related
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Which objects or subtypes from the origin
table can be related to which objects or
subtypes in the destination table
Specify a valid cardinality range for related
objects or subtypes
Relationship Rule Example
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Wood poles are able to support from 0
to 3 transformers, whereas steel poles
support 0 to 5 transformers
In Summary
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Modeling closer to real world by creating
attribute domains, subtypes, and relationship
classes
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Attribute domains define the allowable values
Subtypes provide a way to implement different
domains and relationships
Relationship classes create a permanent record of
their relationship (as opposed to join/relate)
Relationship rules control which objects or
subtypes from the origin table can be related to
which objects or subtypes in the destination table
3-Dimensional GIS
TINs, DEMs and 3-D Surfaces
Surface Analysis in GIS
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Analyzing the distribution of a variable
which can be represented as the third
dimension of spatial data
Elevation is a good example of a 3rd
dimensional variable
Most GIS packages represent z-values
as an attribute of the data
What is a DEM?
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DEM = digital representation of a topographic
surface (usually a raster or regular grid of
spot heights)
DTM or digital terrain model = more generic
term for any digital representation of a
topographic surface, but not widely used
DEM is the simplest form of digital
representation of topography and the most
common
Resolution is a critical parameter
Creating DEMs
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From contour lines (digital or scanned)
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scanning, raster to vector conversion +
additional elevation data are (i.e.
shorelines provide additional contours)
algorithm is used to interpolate elevations
at every grid point from the contour data
Creating DEMs
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By photogrammetry
(manually or automatically)
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extraction of elevation from photographs is
confused when the ground surface is
obscured e.g. buildings, trees
DEMs from each source display
characteristic error artefacts
Background of TINs
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Developed in the early 1970's as a
simple way to build a surface from a set
of irregularly spaced points …..
.....Commercial systems using TIN began
to appear in the 1980's as contouring
packages, some embedded in GISs
Surface Analysis
in a Vector GIS
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Several ways of building a TIN are
possible:
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from a set of irregularly-spaced points
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from points in a regular fashion - a lattice
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from digitized contours as line features
Not usually practical to use polygon
features
The TIN Model
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Sample points are connected by lines to
form triangles
Each triangle's surface would be defined
by the elevations of the three corner
points
Pros and cons of TINs
TIN Construction
From Points to Surfaces
Exaggerating Elevations
Terrain Analysis in Concert
With Other GIS Operations
Calculating Slope
and Aspect
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From (raster) DEMs:
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to estimate these at a raster point, a 3x3
window centered on the point is usually
used
From TINs: simpler and more efficient,
but perhaps not as accurate
What Is Slope?
Slope and Aspect
Calculation
Determining Drainage
Networks
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A raster DEM contains sufficient information
to determine general patterns of drainage
and watersheds
Flow direction determined by the elevations
of surrounding cells
Algorithms to determine the flow direction
Water is assumed to flow from each cell to
the lowest of its neighbors
Flow Direction
DEM
Leading to Flow
Accumulation
Three Steps in Developing
a Hydrological Model
Flow Directions
Accumulating Flow
Critical Flow Level 2
Very Important Points
Relief Shading
Different Techniques for
Visualizing Elevation
2D elevation raster Transparent hillshade Shaded relief map
Main Uses of
DEMs and TINs
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Determining attributes of terrain
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Finding features on the terrain
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elevation at any point, slope and aspect
drainage basins and watersheds, drainage
networks and channels, etc.
Modeling of hydrologic functions
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energy flux and forest fires