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GTECH 361. Lecture 10 Behavior and the Geodatabase. Rules and Behavior. ..is what makes geodatabase features smart Enforcing integrity with attribute domains Grouping features using subtypes Table relationships Between feature classes Between feature classes and non-spatial tables. - PowerPoint PPT Presentation
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GTECH 361
Lecture 10
Behavior and the Geodatabase
Rules and Behavior ..is what makes geodatabase
features smart Enforcing integrity with attribute
domains Grouping features using subtypes Table relationships
Between feature classes Between feature classes and non-
spatial tables
Attribute Domains Define what values are allowed for
a field in a feature or a non-spatial table
Created and edited in ArcCatalog
Attribute Domains
Are a specialization of well-known data types ValveTypeDomain is a Long Integer with a
permissible value range from 1..10
Enforcing Data Integrity
Preventing errors during data entry Checking validity after the fact
Types of Attribute Domains
Range domains
Coded value domains
Split and Merge Policies
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
Duplicate
Default value
Geometry ratio
Merge Policies Default value
Sum
Weighted average
Field Type Limitations to Split and Merge
Policies
Field Types
Split Policy Options
Merge 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
The closest we get to object-orientation in the geodatabase
To group similar features without creating a new feature class 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
ArcView Only displays subtypes
ArcEditor, ArcInfo Create, edit and use subtypes
Example of a Subtype
Subtypes of feature class country_lanes
Example of a Subtype
Subtype encoding and decoding
Feature class table ArcMap Table ofContents
Creating a Subtype Based on an existing attribute, or A new field containing subtype
values 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…
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 Require primary and foreign key to
be of the same type Supported field types are
short integer long integer float
double text object ID
Relationship Classes
Permanently stored in the geodatabase 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
Cardinality, origin and destination tables
As discussed before
Labels
Relationship types and messaging
Attributes
Relationship Labels Relationship classes have forward
and backward path labels
Relationship Types
SimpleTable objects exist independently of each other
CompositeDestination objects cannot exist without an origin object Forward messaging only One-to-one or one-to-many cardinality
Relationship Attributes
Relationship classes can have attributes describing the relationship 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 related objects
Querying, selecting
Querying, labeling, symbolizing
Referential Integrity
Yes No No
Messaging Yes No No
Attributes Yes No No
Relationship Rules
Yes No No
Cardinality All All One-to-one, many-to-one
Relationship Rules
Control how records in the origin and destination tables can be related
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
Wood poles are able to support from 0 to 3 transformers, whereas steel poles support 0 to 5 transformers
In Summary Modeling closer to real world by creating
attribute domains, subtypes, and relationship classes 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 GISTINs, DEMs and 3-D Surfaces
Surface Analysis in GIS
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?
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
From contour lines (digital or scanned)
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 By photogrammetry
(manually or automatically)
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
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
Several ways of building a TIN are possible:
from a set of irregularly-spaced points
from points in a regular fashion - a lattice
from digitized contours as line features
Not usually practical to use polygon features
The TIN Model
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
From (raster) DEMs:
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
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
DEM
Flow Direction
Leading to Flow Accumulation
Flow Directions Accumulating Flow Critical Flow Level 2
Three Steps in Developing a Hydrological Model
Very Important Points
Relief Shading
2D elevation raster Transparent hillshade Shaded relief map
Different Techniques for Visualizing Elevation
Main Uses of DEMs and TINs
Determining attributes of terrain elevation at any point, slope and
aspect
Finding features on the terrain drainage basins and watersheds,
drainage networks and channels, etc.
Modeling of hydrologic functions energy flux and forest fires