GIS Development: Step5 - DB Planning and Design Step6 - Database Construction Step7 -...

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 ScienceUniversity of Indonesia

Dr. Aniati Murni

Copyright ©AniatiMurni

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GIS Development CycleGIS Development Cycle

NeedsAssessment

ConceptualDesign

DatabasePlanningand DesignAvailable

Data Survey

Pilot / Benchmark

HW and SW Survey

DatabaseConstruction

Acquisition ofGIS HW andSW

GIS SystemIntegration

Application

Development

GIS Use and

Database

Maintenance

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.

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Step 5: DB Planning and DesignStep 5: DB Planning and Design

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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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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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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Entities, Attributes, and Spatial Object

DeepOcean

Shelf

UpperSlope

RiseLowerSlope

Plateau orTerrace

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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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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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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 ConstructionStep 6: GIS Database Construction

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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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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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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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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Three basic entities of the geographical object data (Point-Line-Area)

Source:

Purwadhi

(1997)

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GIS Data Model

Graphics Data Index

• 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.

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Raster Data (pixels)

Raster GIS Data

Graphics Grid / Raster Value Attribute Table

2 2 2 2 3 3

2 2 2 3 3 3

2 2 3 3 3 3

2 5 5 5 5 3

5 5 5 5 5 5

5 5 5 5 5 5

Cell ValueReal World Entity

2 Lake

3 Wooded

5 Built-up

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Vector GIS Data

Vector GIS Data

Vector GIS Polygon Layer Polygon Attribute Table

Polygon Identity AttributeNumbet

1 Lake

2 Wooded

3 Built-up

1 2

3

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Step 7: Pilot / BenchmarkStep 7: Pilot / Benchmark

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.DeepOceanRise

LowerSlope

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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.DeepOceanRise

LowerSlope

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Step 7: Pilot /BenchmarkStep 7: Pilot /Benchmark 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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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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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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