Download GIS Development: Step5 - DB Planning and Design Step6

GIS Development:
Step5 - DB Planning and Design
Step6 - Database Construction
Step7 - Pilot/Benchmark
(Source: GIS AsiaPacific, June/July & August/September 1998; and
New York State Archives GIS Development Guides)
Faculty of Computer Science
University of Indonesia
Dr. Aniati Murni
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GIS Development Cycle
Needs
Assessment
Conceptual
Design
Available
Data Survey
The GIS development cycle is based on the philosophy that
one first decides what the GIS should do and then as a
second activity decides on how the GIS will accomplish
each task.
Database
Planning
and Design
GIS
System
Integration
Pilot /
Benchmark
HW and
SW Survey
Database
Construction
Acquisition of
GIS HW and
SW
Application
Development
GIS Use and
Database
Maintenance
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Step 5: DB Planning and Design (1)
• Activities include the followings:
Select a source (document, map, digital file, etc.) for each
entitiy and attribute included in E-R diagram;
Set-up the actual database design (logical and physical
design);
Define the procedures for converting data from source media
to database;
Define procedures for managing and maintaining the
database.
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Step 5: DB Planning and Design (2)
• The quality of information
Information is stored in a database;
Bad construction and data error will give Garbage instead of
Geographic Information System;
What kind of map projection will be used;
What scale is the data;
What is the coverage;
How much attribution should be included;
What is the attribute data format;
What is the data reliability;
How fast is it to be retrieved.
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Step 5: DB Planning and Design (3)
• Information required for database design:
A complete list of data, properly defined and checked for
validity and consistency (from the master data list, E-R data
model, and metadata entries);
A list of potential data source (maps, aerial photos, tabular
files, digital files) cataloged and evaluated for accuracy and
completeness (from available data survey);
The list of functional capabilities required from the GIS
(from needs assessment). Such as visualization, spatial
analysis, statistical analysis and modeling.
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Step 5: DB Planning and Design (4)
Entities,
Attributes,
and Spatial
Object
Plateau
or
Terrace
Lower
Deep
Rise
Slope
Ocean
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Step 5: DB Planning and Design (5)
• Plan for data sharing
Benefits of data sharing include: (i) the development of much
larger database for far less cost; (ii) the development of more
efficient interaction between public agencies; and (iii) all
agencies shared the same up-to-date database / information.
Database maintenance requires two efforts: ongoing user training
(how to maintain the database) and user support (who will be
responsible for updating which data).
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Step 5: DB Planning and Design (6)
• Designing the Database
Most of databases in GIS software packages are
based on the relational database model;
Two choices of using data table: as much data in one
table or small/compact data in one table;
How you will represent the data: point, line,
polygon, network, etc.
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Step 5: DB Planning and Design (7)
• Spatial Database
In the past, all Database System does not include
spatial data; today Oracle already has Spatial Data
Cartridge.
In GIS spatial data (point, line, polygon) can be
used simultaneously. The data is stored using an
index system.
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Step 6: GIS Database Construction (1)
 Database construction can be divided into
two major activities:
 creation of digital files from maps, air
photos, tables, and other source documents;
 organization of the digital files into a GIS
database.
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Step 6: GIS Database Construction (2)
• Database construction/conversion is the process of building the
digital database from the source data - maps and tabular files.
• The main emphasis is management of the activity and quality
assurance / quality control of the converted data.
• Close and effective management is critical factor in successful
data conversion, where the conversion process is often
“contracted out” and involves large quantities of source maps
and documents.
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Step 6: GIS Database Construction (3)
• Data Conversion
– Manual digitizing using a digitizing tablet and cursor tool (puck);
– Scanning (converts lines and text into series of pixels);
– Raster to Vector Conversion (convert series of pixels into series of (x,y)
coordinates points), this facility is usually provided by a GIS software;
– Hybrid solution (overlaying vector format data with an image provides a
powerful graphic display tool;
– Entry of attribute data is done by joining a table of new attributes to an
existing table already in the GIS;
– Acquisition of external digital data (integrating existing database with GIS
should be carefully considered before buying a GIS system).
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Step 6: GIS Database Construction (4)
• GIS HW and SW for Data Conversion (digitizing and editing):
– Digitizing station: precision digitizing tablet, high resolution display terminal
for digitizing, querying, displaying and editing data;
– Editing workstation: is used for QA/QC functions of conversion, has the same
capability as digitizing station except for digitizing;
– Graphic data review / tabular data input workstation: is used for displaying and
reviewing graphic data and for entering tabular attribute data associated with
this graphic feature;
– Digitizing station: precision digitizing X terminal: allows for graphic display
and input of data utilizing the X Window System communication protocol.
• The data conversion can be done in-house or out-contracted.
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Step 6: GIS Database Construction (5)
• Three basic entities of the geographical object data (Point-LineArea)
Source:
Purwadhi
(1997)
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Step 6: GIS Database Construction (6)
• GIS Data Model
• Map graphics represent all of the features (entities) on a map as
points, lines, areas, or pixels;
• Tabular databases contain the attribute information which describe
the entities (building, parcel, etc.);
• A common key (graphics data index) must be established between
the map graphics and the tabular database records to create a link.
Graphics Data Index
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Step 6: GIS Database Construction (7)
• Raster Data (pixels)
Raster GIS Data
Graphics Grid / Raster
2
2
2
2
3
3
2
2
2
3
3
3
3
3
3
2
2
3
2
5
5
5
5
3
5
5
5
5
5
5
5
5
5
5
5
5
Value Attribute Table
Cell Value Real World Entity
2
Lake
3
Wooded
5
Built-up
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Step 6: GIS Database Construction (8)
• Vector GIS Data
Vector GIS Data
Vector GIS Polygon Layer
2
1
3
Polygon Attribute Table
Polygon
Numbet
Identity Attribute
1
Lake
2
Wooded
3
Built-up
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Step 7: Pilot / Benchmark (1)
• Pilot Study and Benchmark Tests
To demonstrate the functionality of the GIS software.
To show what the commercial GIS from the vendor can do.
To demonstrate to potential users and management what the
GIS will do for them.
To show that the performance data of the GIS system can be
determined.
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Step 7: Pilot / Benchmark (2)
• Objectives of A Pilot Study
A pilot study is a focused test to prove the utility of GIS within
a local unit;
It is not a full GIS implementation;
It is not a GIS demonstration;
It is a test of how GIS can be deployed within an organization
to improve operations.
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Step 7: Pilot /Benchmark (3)
• Benchmarking a System:
 A benchmark is the process of testing various combination of hardware and
software, and evaluating their functionality and performance. This test is
usually important for short listed vendors. The same data set should be used to
test all hardware software configuration.
 Get a committee of 8-10 members to set up the benchmark test.
 The tasks performed by the vendor should be measureable (time, ease of use,
can the function be done, etc.), rating various aspects of the system, and rating
also the vendor (teamwork, communication, technical skills).
 Send out the outlines of task the vendor should do in the benchmark test
including the setting up time, task performing time, how many people allowed
to be in the testing process.
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Step 7: Pilot / Benchmark (4)
• Planning a pilot study includes:
creating a sample of the database;
testing the quality of source documents;
testing applications;
testing data management and maintenance procedures;
estimating data volumes;
estimating costs for data conversion;
estimating costs for staffing training.
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Step 7: Pilot / Benchmark (5)
• Procedures for carrying out a pilot study:
 select applications from needs assessment;
 determine study area;
 review conceptual database design;
 determine conversion strategy;
 develop physical database design;
 procure conversion services and develop conversion work plan;
 commence source preparation;
 develop acceptance criteria and qc plan;
 develop data management and maintenance procedures;
 test application;
 evaluate and quantify results;
 prepare cost estimates.
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