Societal Issues
(privacy, surveillance, ethics)
e.g., Google StreetView
Google Maps Mania Blog
Early and late May 2008
More surveillance
(electronic, video, biological,
chemical)
integrated into national system
From Chris Peterson, Foresight
Institute
As presented at OSCON 2008,
Portland
Sewer monitoring has begun
“The test doesn’t screen people directly but
instead seeks out evidence of illicit drug
abuse in drug residues and metabolites
excreted in urine and flushed toward
municipal sewage treatment plants.”
From Chris Peterson, Foresight Institute
As presented at OSCON 2008, Portland
“Citizen
Sensors”
UCLA Center for Embedded Networked Sensing, http://peir.cens.ucla.edu
Lecture 10
Geographic Databases
Gateway to Spatial Analysis
Definitions
Database – an integrated set of
attributes on a particular subject
Geographic (=geospatial) database –
set of attributes on a particular subject
for a particular geographic area
Database Management System (DBMS)
– software to create, maintain and
access databases
cell towers
+/- 500 m
Google db of
tower locations
Wi-Fi
+/- 30 m
iPhone GPS
+/- 10 m
iPhone uses
reference network
db
Graphic courtesy of Wired, Feb. 2009
Skyhook
servers and db
A GIS can answer the question:
What is where?
WHAT: Characteristics of
features (= attributes).
WHERE: In geographic space.
A GIS links attribute and spatial data
Attribute Data
• Flat File or DBMS
• Relationships
• Topology Table
Map Data
• Point File
• Line File
• Area File
• Topology Type
Flat File or DBMS
Attribute
Attribute
Attribute
Record
Value
Value
Value
Record
Value
Value
Value
Record
Value
Value
Value
Types of DBMS Models
Hierarchical
Network
Relational - RDBMS
Object-oriented - OODBMS
Object-relational - ORDBMS
Historically, databases were
structured hierarchically in flat
files...
Relational Databases rule now
2/1/98
2/4/98
Role of DBMS
System
Task
Geographic
Information
System
•
•
•
•
•
Data loading
Editing
Visualization
Mapping
Analysis
Database
Management
System
•
•
•
•
Storage
Indexing
Security
Query
Data
“Programmable API”
Relational DBMS (1)
Data stored as tuples (tup-el),
conceptualized as tables
Table – data about a class of objects
Two-dimensional list (array)
Rows = objects
Columns = object states (properties,
attributes)
Table
Row = object
Vector feature
Column = attribute
Relational DBMS (2)
Most popular type of DBMS
Over 95% of data in DBMS is in RDBMS
Commercial systems
Microsoft Access
Microsoft SQL Server
Oracle
IBM DB2
Informix
Sybase
Relational Join
Fundamental query operation
Occurs because
Data created/maintained by different users, but
integration needed for queries
Table joins use common keys (column
values)
Table (attribute) join concept has been
extended to geographic case
Relational Databases
2/1/98
2/4/98
SQL
Structured (Standard) Query Language –
(pronounced SEQUEL)
Developed by IBM in 1970s
• Standard for accessing relational databases
Three types of usage
Stand alone queries
High level programming
Embedded in other applications
Types of SQL Statements
Data Definition Language (DDL)
Create, alter and delete data
CREATE TABLE, CREATE INDEX
Data Manipulation Language (DML)
Retrieve and manipulate data
SELECT, UPDATE, DELETE, INSERT
Data Control Languages (DCL)
Control security of data
GRANT, CREATE USER, DROP USER
Spatial Query/Search & Retrieval:
Gateway to Spatial Analysis
Overlay is a spatial retrieval operation
that is equivalent to an attribute join.
Buffering is a spatial retrieval around
points, lines, or areas based on
distance.
Overlay
Image courtesy of K. Foote/M. Lynch, UT-Austin
Overlay like an attribute join
2/1/98
2/4/98
Types of overlay operations
Union
Intersect
Identity
Max
Min
Etc.
Union
computes the geometric intersection of two
polygon coverages. All polygons from both
coverages will be split at their intersections
and preserved in the output coverage.
Union
within 25 miles of
a city OR within
25 miles of a
major river.
Intersect
computes the geometric intersection of two
coverages. Only those features in the area common
to both coverages will be preserved in the output
coverage.
Intersect
within 25 miles of
a city AND within
25 miles of a
major river.
Identity
computes the geometric intersection of two coverages. All
features of the input coverage, as well as those features of the
identity coverage that overlap the input coverage, are preserved
in the output coverage.
Identity
Portion of the major city buffer WITHIN the major river buffer
within 25 miles of a city OR within 25 miles of a major river.
within 25 miles of a city AND within 25 miles of a major river.
Intersect
Identity
Raster Retrieval: Map Algebra
Raster overlay
Combinations of spatial and attribute
queries can build some complex and
powerful GIS operations.
Input Grid A
Input Grid B
Compared
with
Output Grid C
Buffer
Recode
OR
And many more ….
See spatial analysis handout on course
web site.
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Lecture 10 Creating and Maintaining Geographic Databases