1. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. Akm Saiful Islam WFM 6202: Remote Sensing and GIS in Water Management Akm Saiful Islam [Part-B: Geographic Information System (GIS)] Lecture-4: Spatial Database December, 2006 Institute of Water and Flood Management (IWFM) Bangladesh University of Engineering and Technology (BUET)

2. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. Akm Saiful Islam Concept of Spatial Database A spatial database is defined as a collection of inter- related 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.

3. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. 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:  definition of database contents  selection of database structure  data distribution to users  maintenance and updating control  day-to-day operation

4. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. 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.

5. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. Akm Saiful Islam Storage media

6. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. Akm Saiful Islam Partition of Spatial Data

7. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. Akm Saiful Islam Spatial Data Models 1.Hierarchical 2.Network 3. Relational 4. Object oriented

8. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. Akm Saiful Islam 1. Hierarchical Model Stores data as hierarchically related to each other. Record shape are tree structure. BUET Faculty of Civil Engineering Faculty of Architectural CE WRE URP Archit.

9. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. 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 IslamDr. Akm Saiful Islam

10. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. 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.

11. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. 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 ID NameCourseID 1Mr. X001 2Mr. X002 3Mr. Y003 Cour seID TitleCre dit 001RS & GIS in WM3 002Watershed Hydrology3 003Risk Management3 Course table Student Table Course Table * * Many to many relationship

12. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. Akm Saiful Islam Relational Database 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.

13. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. 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

14. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. Akm Saiful Islam Find the relationship between this two tables in the BUET Library ISBNTitleAuthor 050Applied Hydrology David Maidmen 060IrrigationCheng IDNameISBN 1Mr. P050 2Mr. Q060 3Mr. R070 Book Table Borrow Table One to one Many to Many One to Many ?

15. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. Akm Saiful Islam Normalization of an Un-normalized Table to relational database

16. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. 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.

17. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. Akm Saiful Islam 4. Object Oriented Model BUET DepartmentsInstitutes CE WRE DCEIWFM URP AIT Faculty, Staff, Students Attributes: Is a Is a = Inheritance Part of = association Part of

18. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. 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.

19. WFM 6202: Remote Sensing and GIS in Water Management © Dr. Akm Saiful IslamDr. Akm Saiful Islam Example of Object Oriented Model