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3. Coordinate System Transformation 4. DMBS and its use in GIS

Lecture 15: GIS Database Creation and Maintenance (III). Topics. 3. Coordinate System Transformation 4. DMBS and its use in GIS. Readings on the topics. Chapter 5 in Longley et al. 2005, pp. 123-125 Chapter 10 in Longley et al. 2005 Goodchild, M.F., 1984. “Geocoding and Geosampling,”

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3. Coordinate System Transformation 4. DMBS and its use in GIS

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  1. Lecture 15: GIS Database Creation and Maintenance (III) Topics 3. Coordinate System Transformation 4. DMBS and its use in GIS Readings on the topics • Chapter 5 in Longley et al. 2005, pp. 123-125 • Chapter 10 in Longley et al. 2005 • Goodchild, M.F., 1984. “Geocoding and Geosampling,” • In: G.L. Gaile and C.J. Willmott (eds.), Spatial Statistics • and Models Other Readings • Chapter 6 in Aronoff’s, 1993, pp. 180-186 • Chapter 3 in Burrough and McDonnell’s, 1998, pp. 50

  2. Outlines 3. Coordinate Transformation: • 3.1 Between two known plane coordinate systems - Affine Transformations (Linear Transformations): • 3.1.1 Simple Affine (Simple Affine Figure) • 1) Translation • 2) Rotation • 3) Scaling • 3.1.2 Complex Affine

  3. 3.2 Between an unknown system to a known system – Rubber Sheeting (Polynomial Transformations, Statistical Space Transformations): • 3.2.1 Basic idea of rubber sheeting: • Extract the relationship between two coordinate systems through a set of control points and apply the relationship to convert other points into the known coordinate system • X Y U V • P1 x1 y1 u1 v1 • P2 x2 y2 u2 v2 • …… • Pn xn yn un vn • 3.2.2 Choosing initial control points • 1) Where (which)? • 2) How many? • 3) Spatial distribution

  4. 3.2 Between an unknown system to a known system – Rubber Sheeting: (continued…) • 3.2.3 Refining control points • 1) Computing error • X Y U V U’ V’ Eu Ev E • P1 x1 y1 u1 v1 u1’ v1’ Eu1=u1’-u1 Ev1=v1’-v1 E1=sqrt(Eu12+Ev12) • P2 x2 y2 u2 v2 u2’ v2’ Eu2=u2’-u2 Ev2=v2’-v2 E2=sqrt(Eu22+Ev22) • …… • Pn xn yn un vn un’ vn’ Eun=un’-un Evn=vn’-vnEn=sqrt(Eun2+Evn2) • RMSE: sqrt((E12 + E22 + … + En2) / n) • 2) Refining control points • Step1: Checking RMSE, if satisfied, done; • Step2: Deleting points based on error of each control point; • Step3: Rerun the rubber sheeting, start over from Step1. • 3. 3 Geocoding • Process of assigning map coordinates to spatial entity.

  5. 4. DBMS and its use in GIS: • 4.1 Basic Concepts: • 4.1.1What is a database? • A database is a collection of information about things and their relationships to each other. The objective in collecting and maintaining information in a database is to relate facts and situations that were previously separate so that integrated analysis is possible (The Student Table) • 4.1.2 Managing conventional databases • 1) The file access approach • 2) The DBMS approach

  6. 4.1 Basic Concepts: • 4.1.2 Managing conventional databases • 1) The file access approach • A) Definition: • with a file access approach, special purpose programs (application programs) directly access each data file that they use in a database. These special purpose programs need to know exactly how the data in each file are stored (File Access Approach) • B) Drawbacks: • (a) Redundancy: the instructions to access a data file must be present in each application program. If modifications are made to the data file, modifications are also need for all application programs that use the data file • (b) Lack of central control: data integrity

  7. 4.1 Basic Concepts: • 4.1.2 Managing conventional databases • 2) The DBMS approach • A) Definition: • A data base management system (DBMS) is comprised of a set of programs that manipulate and maintain the data in a data base (storing, sorting and retrieving). They were developed to manage the sharing of data in an orderly manner and to ensure that the integrity of the data base is maintained (DBMS Approach) • B) Pros and Cons: • (a) Pros: • - Centralized control • - Data independence • - Efficient data sharing • (b) Cons • - High cost • - Added complexity • - Centralized risk

  8. 4.2 DBMS and its use in GIS: • Managing both spatial and attribute data. • 4.2.1Unique aspects of Spatial Databases (Storage of GIS): • 4.2.2 Types of DBMS in GIS (Type of DBMS): • 1) File access system • 2) Hybrid system • 3) Extended DBMS • 4) Integrated (custom designed) system

  9. Questions: 1. When do we use Affine Transformation and when do we use Rubber Sheeting to perform coordinate transformation? 2.How to choose initial control points and how to refine control points in Rubber Sheeting transformation? 3.Compare and contrast file access approach and DBMS approach to manage conventional databases. 4.What are the unique aspects of spatial database and what are the common types of DBMS used in GIS?

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