Transcript Master_first_six

Features, Formats &
Attributes
GIS 458
Spring 2006
Layer Types
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Vector
Raster
Terrain and Other Surfaces
Other
• Addresses
• Geoprocessing Models
• Survey Data
• Networks
Vector Data
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Discrete Data
Have precise shape and position
Best for defined shapes and
boundaries
Have attributes and behavior
Points
• Zero-Dimensional
• Features too small to be lines or areas
• Stored as single x,y coordinates
Vector Data
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Lines
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One-Dimensional
Features too narrow to be areas
Stored as series of ordered x,y coordinates
Segments:
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Straight
Circular
Elliptical
Splined
Polygons
• Two-Dimensional
• Features that cover a broad geographic area
• Stored as series of segments that enclose an area
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Annotation
• Descriptive labels
• Associated with features
• Display names and attributes
Raster Data
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Gridded data composed of cells or pixels
(picture elements)
Two-Dimensional
Values can depict various data
• Light values (spectral)
• Elevation (thematic)
• Density (thematic)
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Discrete or Continuous
Can also be stored in an attribute field
• Photo of a building
Terrain & Other Surfaces
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Triangulated Irregular Network (TIN)
Model of a surface
Stored as:
• Integrated nodes
• Triangles with edges
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Enable surface analysis
Cannot be stored directly in
geodatabase
Other Layer Types
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Addresses
• Data stored in database
• “Locators” create features for locations
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Geoprocessing Models
• You create tools and store them
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Survey Data
• Data tables tied to feature coordinates
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Networks
• Require connectivity & topology
Attributes
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Quality of an object
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Size
Density
Name
Flow
Date
Population
A feature can have a number of attributes
Allow analysis & symbolization
GIS 458
Spring 2006
Instructor: Larry Clamp
Course Topics
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Design Process
Layer Design & Formats
• Raster vs. Vector
• Point, Line or Polygon?
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Relationships
• Spatial
• Non-Spatial
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Attribute Table Design
• Defining Appropriate Fields
• Assigning Appropriate Field Types
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Text, Integer, Double…
Course Topics, continued
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Database Fundamentals
• Purpose
• Personal vs. Enterprise
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Database Design
Database Implementation
Course Topics, continued
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Software Selection
• Database software (Oracle, SQL, etc.)
• GIS Software…is ESRI the best?
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Data Standards
• FGDC
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Personnel
Project Management
Data Mining
BREAK!!!!
GIS (Geographic Information
System)
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Consists of:
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Computer hardware
Software
Geographic data
Personnel
Is a computer system that stores and links
geographically-referenced information with
graphic map features to allow a wide range of:
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Information processing and retrieval
Display operations
Map production
Analysis, and
Modeling
Benefits of a GIS (Functionality)
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Data entry/updating: access the database to
update, add or delete information
Data conversion: take diverse information,
formats, etc. and make them compatible
Data retrieval: take massive amounts of
stored information and access it
Data manipulation: select via query and
classify (symbolize) in different manners
Data presentation: present retrieved
information in either text, tabular or map
format.
Spatial analysis: take spatial data and make
queries (from simple to complex) and
generate new data from the original set
Three general operations in a GIS:
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1. Attribute queries (aspatial queries):
• How many parcels in an attribute table are
zoned R-7 and what is their total acreage?
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2. Spatial queries:
• How many pulp plants are located within
500 meters of a river?
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3. Generation of new data sets from
the original database:
• Out of a marine mammal dataset, where
are just the Beluga whales located?
• Are there areas where ring seals and orcas
overlap?
What is “Spatial Data”?
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Spatial means it is “mappable”, that is,
every piece of information is attached to a
specific object on the map and that
object’s location on the map is
geographically-referenced
Reference systems typically use
latitude/longitude, UTM, SPC or some type
of x,y coordinate system
Where do we get “Spatial Data”?
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From a variety of sources:
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U.S. census
Land use surveys
Satellite imagery
Aerial photographs
Paper maps
Problem: compatibility
• Projections/coordinate systems--Albers
Equal-Area Conic vs. UTM
• Map scale--1:2,000 vs. 1:2,000,000
• Data formats--DRG, (raster), Shapefile
(vector)
Examples of GIS Data
Structures
Organizing Geographic
Data
GIS 458
Spring 2006
Larry Clamp
Parts of the Whole
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Geodatabase
Geographic Datasets
Object Classes
Feature Classes
Topological Classes
Relationship Classes
Geodatabase
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A collection of data types
• Datasets & feature, object and relationship
classes
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Can span one, several, or many
geodatabases
Manage seamless geographic data
Two main types
• Personal
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Represent small to medium-sized datasets
• Enterprise
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Represent large or complex datasets (multiple users)
Geographic Datasets
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Feature Dataset
• Collection of feature classes
• Common coordinate system
• FC’s must be in FD’s for topology
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Raster Dataset
• Simple (basic GRID)
• Compound (multiple bands, etc.)
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Triangulated (TIN) Dataset
Object Classes
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Table that can associate behavior
Descriptive information about objects
• Owners
• Stream Codes
• Annotation
Feature Classes
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Collection of features with same
geometry
• Points, lines, polygons
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Simple feature classes
• No topology
• Features are independent of one
another
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Topological feature classes
• Features are bound to one another
• Share certain behavior
Relationships
Relationships
No…Seriously
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Relationship class
• Table that stores realtionships between
features or objects
• Models dependencies between objects
• Can control what happens to related
objects
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Removed
Changed
Keep it Simple…
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Geodatabase = Filing Cabinet
• Feature Dataset = Filing Cabinet Drawer
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Feature Class = Individual Folder in Drawer
Sub-Types & Attribute
Domains
GIS 458
Spring 2006
Larry Clamp
Sub-Types
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Objects (rows) in a table or feature class
grouped by an attribute
• Roads by class: Highways, major roads,
arterials, etc.
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Allow users to make validation rules more
specific to data
Help insure data quality
Speed up data entry and editing
Help eliminate need for additional classes
• Wells: Different class for public, agricultural or
monitoring wells or
• Just different sub-types?
Sub-Types, continued
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Based on integer attribute field
Integer codes and descriptions
entered
Editor constrained to entered values
In ArcMap, description is displayed
Description used for labeling
Setting Sub-Types
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Set as properties of an existing table
or feature class
Go to Properties dialog
Select integer sub-type field
Input code and description
Can also set defaults and domains
Attribute Domains
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Define legal field values for tables, feature
classes, or sub-types
Defined as properties of the geodatabase
Can be shared across the geodatabase
Assigned to fields by editing field
properties of tables & feature classes
Do not constrain incorrect data entry but
will find errors
• Validation tool on Editor menu
Legal Values
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Two Types of domains
• Range and Coded Values
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Type used depends on nature of
attribute data
Range vs. Coded Values
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Range domains
• Apply to values for numeric attributes
• Used for measured data
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Well depth
Contamination levels
Power pole heights
• Legal minimum and maximum
Range vs. Coded Values
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Coded values
• Apply to any type of attribute
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Text, numeric, date, etc.
• Used for coded data
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Land-use codes
Water pipe material codes
Street surfacing codes
• Define list of legal codes and their
descriptions
Splitting & Merging Features
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Domains allow you to define how
attributes are handled during
splitting & merging
Split policy
Merge policy
Split Policies
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Defines what values are assigned to
resulting features
• Default value
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Each take on a default value you set
• Duplicate value
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Each take on a copy of original value
• Geometry ratio
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Each take on a ratio of the original value
Merge Policies
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Dictates what happens to values of
merged features
• Default value
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Each take on a default value you set
Only policy that applies to nonnumeric fields
and coded value domains
• Sum
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Sum of the original features
• Geometry weighted
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Weighted average of original features
Summary
Field Types
Domain Type
Split Policies
Merge Policies
Double, Float,
Long Integer,
Short Integer,
Date, Text
Coded Value
Default value,
Duplicate
Default value
Range
Default value,
Duplicate,
Geometry ratio
Default value,
Sum,
Weighted
average
Double, Float,
Long Integer,
Short Integer,
Date
Table Design &
Importing Data
GIS 458
Spring 2006
Larry Clamp
Ways to create tables
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ArcCatalog
• Right click location
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Folder, geodatabase…
• Select New>Table to access wizard
• You can import fields from other tables
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Geoprocessing (ArcToolbox)
• Under Data Management Tools
• Select Table toolset > Create Table
Table Field Properties
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Alias
Allow NULL Values
Default Value
Domain
OBJECTID
Length
Precision
Scale
BLOB
Raster
Alias
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Alternate field name for display in
ArcMap
Less cryptic…
Can be changed after the table is
created
Allow NULL Values
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Indicates field may or may not
contain null data
Null value = absence of recorded
value
Different than 0 (which is a value)
May NOT be changed after table is
created
Default Value
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Value that is automatically assigned
for a new record
May be changed after table is
created
Domain
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Assigned geodatabase domain for
field
Defines legal values
Can also define how feature
attributes are handled if they are
merged or split
May be changed after table is
created
OBJECTID
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Automatically generated
DO NOT delete or change it in any
way!!
Length
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Maximum number of characters to
store in text field
Set as an integer
Precision
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Maximum number of digits for a
numeric field
Set as an integer
Scale
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Maximum number of decimal digits
for a decimal numeric field
Set as an integer
BLOB
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Binary large object
Data stored in the geodatabase as a
long sequence of binary numbers
Stores images, multimedia, or bits of
code
ArcGIS doesn’t provide end-user
tools
Must write custom objects or
applications to manage a BLOB field
Raster
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New attribute type
Stores raster within or alongside the
geodatabase
ArcGIS views many file formats but
outputs as a GRID, IMAGINE, or TIFF
Will convert for you
Only one raster field allowed in a table or
feature class
Use a different table with a relate to
associate more
Naming Conventions
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Table name, feature class and field
names must be compatible with
underlying RDBMS
For ESRI this means:
• No spaces
• Use underscores or run words together
• Field names limited to ten characters
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Use an alias for more descriptive name
Data Type
Field Data Types
Bytes
Range
Application
Short
Integer
2
-32,768 to 32,767
Numbers without fractions
within specific ranges; coded
values
Long Integer
4
-2,147,483,648 to
2,147,483,647
Numbers without fractions
within specific range
Float
4
Approx. -3.4E-38 to 1.2E38
Numbers with fractions within
specific range
Double
8
Approx. -2.2E-308 to
1.8E308
Numbers with fractions within
specific range
Text
Varies
Up to 64,000 characters
Names or other textual
qualities
Date
8
Mm/dd/yyy, hh:mm:ss;
AMP/PM
Date and/or time
BLOB
Varies
Varies
Images or other multimedia
Raster
Varies
Stores Images
Storing images
Importing Data (vector data)
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IMPORT tools
• ArcCatalog context menu or
• Geoprocessing tools
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Simple Data Loader (ArcCatalog)
• Loads to existing table or feature class
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Empty or with data)
ArcMap Object Loader
• Loads to existing table or feature class
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Empty or with data)
Work for both personal or enterprise GDB
IMPORT tools
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ArcCatalog menus
• Right click on location to import…
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Geoprocessing tools
• ArcToolbox > Conversion Tools > To
Geodatabasae
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Both use same tools
Simple Data Loader
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ArcCatalog context menus wizard
Loads data into an existing table or
feature class
• Object may be empty or contain data
• Data sources must have same schema
(multiple)
• Feature classes
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Target and source MUST have same
geometry
• Can query to import only selected data
• Geometric networks & versions not
supported
Object Loader
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Accessible only in ArcMap edit session
Must add as a custom tool
• Tools>Customize>Commands>Data
Converters
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Loads “complex data” to table or feature
class
• Supports behavior as it loads
• Object may be empty or contain data
• Data sources must have same schema
(multiple)
• Feature classes
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Target and source MUST have same geometry
• Can query to import only selected data
The Geodatabase
Design Process
GIS 458
Spring 2006
Larry Clamp
Why is Good Design
Necessary?
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Questions to Answer:
• How can we employ GIS technology to:
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Improve existing functions?
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Change goal achievement?
• What data is most beneficial?
• What data can be acquired & stored?
• Who will maintain the database?
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Establish Process to:
• Define goals
• Identify, analyze and evaluate alternatives
Design Objectives
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Avoid risks of lack of design
Satisfy objectives and requirements
Obtain necessary data
Avoid unnecessary redundancy
Organize data for different users
Accommodate different data views
Divide maintenance and users
Appropriate feature representation,
organization & coding
Benefits of Design
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Time consuming…but worth it!
Increased data retrieval & analysis
flexibility
Increased user application
development
Better cost distribution
More users supported
Support for future development
Less data redundancy
Design Guidelines
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Involve Users
One Step at a Time
Build a Team
Be Creative
Create Deliverables & Milestones
Keep Goals and Objectives in Focus
Don’t Add Detail Too Soon
Document Carefully!!!!!!
Be Flexible
Use Model to Plan
Design Steps
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Model the User’s View
Define Entities (features & objects)
and Relationships
Identify Proper Entity (features &
objects) Representation
Match These to the Geodatabase
Model
Organize into Geographic Datasets
Model the User’s View
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Ensure common understanding
between designers and users
Identify Organizational Functions
• Business or service functions &
processes are more stable than business
organization
• What do they do?
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Identify Data Requirements
• Interact!
• Who uses it and what is the nature of
interaction?
Define Entities and
Relationships
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Broad to Narrow
Identify & Describe Entities
• Use detail
• Involve end users!
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Identify & Describe Relationships
• Use descriptive & interpreting
statements
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Use Diagrams to Show E & R
• Unified Modeling Language
Identify Proper Entity
Representation
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Classify by Type of Representation
Will it be used on a map?
Is shape significant for analysis?
Can it be accessed and visualized through
relationship to another feature?
Will it have different representations at
different scales?
Does it need annotation?
Should it be a:
• Point, line or polygon
• A surface, raster, image, photo or drawing
• An object
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No point, line or polygon required
Match to the Geodatabase
Model
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Determine Geodatabase Representation
Simple Features
• Discrete
• No Topology
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Complex Features
• Discrete
• Topology or participation in a network
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Points
Lines
Polygons
Images
Surfaces
Organize into Geographic
Datasets
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Identify & Name Datasets
Group Feature Classes
• Large feature class
• Subtypes
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Custom behavior
Substantially different attributes
Different access requirements
Define Topology Needs
• Feature classes participating in topology
or network must be in the same feature
dataset
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Group in Geodatabase(s)