Transcript GIS and Remote Sensing in Water Resources Management

WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
WFM 6202: Remote Sensing and GIS in Water
Management
[Part-B: Geographic Information System (GIS)]
Lecture-4: Spatial Database
Akm Saiful Islam
Institute of Water and Flood Management (IWFM)
Bangladesh University of Engineering and Technology (BUET)
November, 2008
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
Concept of Spatial Database
• A spatial database is defined as a collection of interrelated geospatial data, that can handle and maintain a
large amount of data which is shareable between
different GIS applications.
• Required functions of a spatial database are as follows.
- consistency with little or no redundancy.
- maintenance of data quality including updating
- self descriptive with metadata.
- high performance by database management system
with database language.
- security including access control.
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
Design of Spatial Database
The design of spatial database will be made by
the database manager who is responsible for
the following issues:
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definition of database contents
selection of database structure
data distribution to users
maintenance and updating control
day-to-day operation
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
Database Design Parameters
The following parameters should be well designed.
• storage media
Volume, access speed and on line service should be
considered.
• partition of data
Choice of administrative boundaries, map sheets, watersheds
etc. will be made in consideration of GIS applications
• standards
Format, accuracy and quality should be standardized.
• change and updating
Add, delete, edit and update should be well controlled by the
database manager.
• scheduling
Data availability, priorities, data acquisition etc. should be well
scheduled.
• security
Copyright, back up system and responsibilities should be well
managed.
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
Storage media
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
Partition of Spatial Data
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
Spatial Data Models
1. Hierarchical
2. Network
3. Relational
4. Object oriented
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
1. Hierarchical Model
• Stores data as hierarchically related to
each other. Record shape are tree
structure.
BUET
Faculty of
Civil Engineering
CE
WRE
Faculty of
Architectural
URP
Archit.
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
Hierarchical Model
• Several records or files are hierachically related with
each other. For example, an organization has several
departments, each of which has attributes such as name
of director, number of staffs, annual products etc.
• Each department has several divisions with attributes of
name of manager, number of staffs, annual products etc.
• Then each division has several sections with attributes
such as name of head, number of staff, number of PCs
etc.
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
Advantage and Disadvantages of
Hierarchical Model
• Advantages
– High speed access to large databases
– Easy to update- (to add or delete new nodes)
• Disadvantages
– Links are only possible in Vertical Direction (from
top to bottom) but not for horizontal or diagonal
unless they have same parents.
– For example, it is hard to find what is the relation
between URP and DCE from this data model.
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
3. Relational Model
• Based on two important
concepts:
– Key of relation - one to
one, one to many, many
to many
– Primary attribute –
which can’t be duplicate
Student
Table
*
*
Course
Table
Many to Many relationship
Student Table
Student
ID
Name
CourseID
1
Mr. X
001
2
Mr. X
002
3
Mr. Y
003
Course table
Cour
seID
Title
Cre
dit
001
RS & GIS in WM
3
002
Watershed Hydrology 3
003
Risk Management
3
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
Relational Database
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Relational database is the most popular model for GIS. For example,
the following relational database softwares are widely used.
- INFO in ARC/INFO
- DBASE III for several PC-based GIS
- ORACLE for several GIS uses
In a relational model, the following two important concepts should be
defined.
Key of relation ; a subset of attributes
Unique identification ; e.g. the key attributes is a phone directory in a
set of last name, first name and address.
non redundancy ; any key attribute selected and tabulated should keep
the key's uniqueness. e.g. address can not be dropped from telephone
address, because there may be many with the same names.
Prime attribute : an attribute listed in at least one key.
The most important point of the relational database design is to build a
set of key attributes with a prime attribute, so as to allow dependence
between attributes as well as to avoid loss of general information when
records are inserted or deleted.
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
Structural Query Language
(SQL)
• SQL is used to perform query in relations databases.
• For example, find the name of the student who took more
than or equal to 6 credit hour in this term
SELECT Student.Name, Course.Credit
FROM Student, Course
WHERE Student.CourseID = Course.CourseID
AND Credit >= 6
• The answer is :
Mr. X 6
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
Find the relationship between this
two tables in the BUET Library
Book Table
ISBN
Title
Author
050
Applied
David
Hydrology Maidmen
060
Irrigation
Cheng
One to one
Many to Many
One to Many
Borrow Table
ID
Name
ISBN
1
2
3
Mr. P
Mr. Q
Mr. R
050
060
070
?
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
Normalization of an Un-normalized
Table to relational database
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
Advantage of Relational Database
 Advantages
 there is no redundancy.
 type of building of an owner can be changed without destroying
the relation between type and rate.
 a new type of building for example "Clay" can be inserted. (row
insert is easy).
 Disadvantages
 Require a number of tables and relationship
 Its difficult to add a new column in the table.
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
4. Object Oriented Model
BUET
Part of
Part of
Departments
Is a
Is a
CE
Institutes
Is a
URP
DCE
IWFM
AIT
WRE
Is a = Inheritance
Part of = association
Attributes:
Faculty, Staff, Students
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
Object Oriented Database
• An Object Oriented model uses functions to model spatial and
non-spatial relationships of geographic objects and the
attributes.
• An object is an encapsulated unit which is characterized by
attributes, a set of orientations and rules. An object oriented
model has the following characteristics.
• generic properties : there should be an inheritance
relationship.
• abstraction : objects, classes and super classes are to be
generated by classification, generalization, association and
aggregation.
• adhoc queries : users can order spatial operations to obtain
spatial relationships of geographic objects using a special
language.
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
Example of Object Oriented Model
WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful Islam
Object based vector data model
• It treats spatial data as object. An object can represent
a spatial feature such as a road or a hydrologic unit.
• Object based database differ from relational database in
two important aspects:
– 1. It stores both spatial and attribute data in a single
system rather than an split system.
– 2. it allows spatial feature (object) to be associated
with a set of properties and methods. A property
describes an attribute or characteristics of an object.
A method performs a specific action.