CE 250 - Introduction to Surveying and G eographic I nformation S ystems
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Transcript of CE 250 - Introduction to Surveying and G eographic I nformation S ystems
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CE 250 - Introduction to Surveying and
Geographic Information Systems
Donald J. Leone, Ph.D., P.E.
eLearning Version
Lecture 3
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Introduction
What are databases and database management systems (DBMS)?
What is a relational data base model?
How are databases linked with GIS? How do we get paper maps into the
computer? How can we edit and convert data?
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Databases Spatial Data – “Where things are” Attribute Data – “What things are” Attribute Data – Stored in databases
Def: Database – “A set of structured data – usually in table form”, or
“ A Collection of related data”
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Traditional Database Example
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Traditional Databases Some Problems
Duplication of Data High Maintenance Costs Data Sharing Difficulties Lack of Security and
Standards
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Computer Based Databases
Different data access methods will be available.
Are independent of application. Unnecessary duplication of data –
minimized. Access controlled and centralized. Maintaining and Updating
relatively easy. Can ask questions - “query”
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Database Approach
Data
Application
Database Management System
Database
DBMS
Hotel
Booking
Travel
Arrangements
Ski School
Booking
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Database Management Systems
Functions File Handling/management Adding/deleting/updating
records Extraction of data (sorting,
querying) Maintenance (security, backup) Application building
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Data Base Table
PIN Owner Address
SaleDate
Acres
Zone Code
Zoning
P101
Wang 101 Oak St. 1-10-98 1.0 1 Res.
P101
Chang 200 Maple St.
1-10-98 1.0 1 Res.
P102
Smith 300 Spruce Rd.
10-6-68 3.0 2 Com.
P102
Jones 100 Ash St. 10-6-68 3.0 2 Com.
P103
Costello
206 Elm St. 3-7-97 2.5 2 Com.
P104
Smith 300 Spruce St.
7-30-78 1.0 1 Res.
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Separate Data Tables – A Relational Database
PIN
PIN Owner name
Owner name
Zone Code
Zone Code
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Creating a New Table
JOIN
Key Field
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Joined Table
PIN Owner Address
P101
Wang 101 Oak St.
P101
Chang 200 Maple St.
P102
Smith 300 Spruce Rd.
P102
Jones 100 Ash St.
P103
Costello
206 Elm St.
P104
Smith 300 Spruce St.
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Creating New Tables – “The Query”
Standard Query Language – SQL Generate New tables Advantages:
Completeness, Simplicity Style, Wide Application
Disadvantages: Slow, Difficult to implement Can’t Handle geographic concepts, i.e.
“near to”
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Parcel Table
PIN SaleDate
Acres
Zone Code
P101
1-10-98 1.0 1
P102
10-6-68 3.0 2
P103
3-7-97 2.5 2
P104
7-30-78 1.0 1
“Which Parcels (PINS) have 2 or more acres?”
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Create a New Table Using SQL
Query: “Acres” =>2.0
Result:PIN SaleDate
Acres
Zone
Code
P102 10-6-68
3.0 2
P103 3-7-97 2.5 2
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Creating a Database
1. Data Investigation – Fact finding.
2. Data Modeling – Relationships between entities and attributes – Define Tables.Define Tables.
3. Database Design – Fit data modeling to software at hand.
4. Database Implementation – Filling in the actual data.
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Data ModelingEntity Attribute Modeling
(EAM)
1. Identification of Entities
2. Identification of the Relationship between entities (1:1, 1:M, M:1, M:N)
3. Identification of the Attributes of the entities
4. Development of the Tables
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EAM for Ski Resort
1. Entitles – Hotels, Travel Companies, Ski Schools, Visitors
2. Relationshipsa) Many visitors stay at One hotel (M:1)b) One Travel Co, organizes for Many visitors (1:M)c) One Ski School teaches Many visitors (1:M)d) Different Travel Co.s may use Different
Ski Schools (M:N)
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EAM DiagramN
a) Many visitors stay at One hotel (M:1) b) One Travel Co, organizes for Many
visitors (1:M) c) One Ski School teaches Many
visitors (1:M) d) Different Travel Co.s may use
Different Ski Schools (M:N)
a
c
d
b
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Attributes of the Entities
HOTEL (Hotel ID, Name, Other Attributes)TRAVEL CO. (Travel Co. ID, Travel Co.
Name, Other Attributes)SKI SCHOOL (Ski School ID, Ski School
Name, Other Attributes)VISITOR (Visitor ID, Visitor Name, Hotel
ID, Travel Co. ID, Ski School ID, Other Attributes)
LINK (Travel Co. ID, Ski School ID)
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Ski
Reso
rt
Tab
les
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Linking Spatial and Attribute Data
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Database Applications
Single
User/PC
Large Corporate Databases
Large Computers
Control Access
Manage Data
Security
Different Sites
Simple Software
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Little Grey Cells Quiz
SQL stands for standard question link. T or F
One of the functions of a DBMS is to
allow several applications access to the data. T or F
Give one advantage of a computer database over a “traditional” database.
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Break!
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Getting the Data Into The Computer
Data Input (Encoding) and Editing
ANALOG DIGITAL What is data encoding?
How are paper maps digitized? How are paper maps scanned?
Methods of Data Editing and Conversion
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Data Capture
Editing/Cleaning
Re-Projection
Generalization
Edge Matching and Rubber Sheeting
Layering
Maps Satellite Data Digital Data Tabular Data Soft Ideas
Digitizing Scanning Data Transfer Key Coding
Integrated GIS Database
Data Editing
Data Encoding
Methods
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Data Encoding Methods
Digitizing Tracing over a map with a cursor.
Mechanical Device with a Human Operator.
Most errors operator induced.
Produces A Vector Map.
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Data Encoding Methods
Scanning
Some problems with scanning (automatic digitizing)
Distortion. Automatic scanning of unwanted
images. Produces a raster image- can be
vectorized with some problems. Amount of editing required to produce
suitable spatial data.
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UT Hall
HJG Center
Sports Center
University of Hartford Aerial Photo
Ground Truthing Points
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ScanningOriginal Paper
Map
Scanned Image
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Data Encoding Methods
Electronic Data Transfer
What data exist? How much they cost? What format will it be in?
Pay off – Considerable time and effort saved!
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Data Editing MethodsDetecting and Correcting
Errors
Missing or Duplicate Features Mislocated Features Missing or Duplicated Labels Unwanted Results of
Digitizing or Scanning Noise
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Errors in Vector Data
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Errors in
Raster Data
Noise
Original “noisy” data
3 x 3 Mean Filter
9 x 9 Mean Filter
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Producing a Common Reference
Re-Projection
Transformation
Generalization
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Producing a Common Reference
Re-ProjectionAll data needs to be referenced to
the same projection.
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Trying to Overlay Different Projections
Cylindrical Conic
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Producing a Common Reference
Re-ProjectionAll data needs to be referenced to the same projection.
TransformationAll data needs to have the same origin.
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Producing a Common Reference
Re-ProjectionAll data needs to be referenced to the same projection.
TransformationAll data needs to have the same origin.
GeneralizationAll data needs to be set to the same scale.
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Remaining Problems After Re-Projection, Transformation, and Generalization
Edge Matching
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Remaining Problems After Re-Projection, Transformation, and Generalization
Rubber Sheeting
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An Integrated DatabaseSki Resort Example
Layer Name Source Data Model
Infrastructure Scanned – 1:5000
Raster
Hotels Survey Data Vector
Ski Schools Survey Data Vector
Weather Stations
GPS Data Vector
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An Integrated DatabaseSki Valley Example
Layer Name Source Data Model
Roads Digitized 1:25000
Vector
Ski Trails DigitizedAerial Photos
Vector
Ski Resort Boundary
Digitized 1:25000
Vector
Topography File Transfer1:25000 DTM
Vector/Raster
Land Use Satellite Image Raster
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Summary
What are databases and data base management systems (DBMS)?
What is a relational data base model?
How are databases linked with GIS? How do we get paper maps into the
computer? How can we edit and convert data?
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What’s Next
Up to now – Data Formation
Data Analysis – Decision Making