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CE 250 - Introduction to Surveying and G eographic I nformation S ystems

CE 250 - Introduction to Surveying and G eographic I nformation S ystems. eLearning Version. Donald J. Leone, Ph.D., P.E. Lecture 3. Introduction. What are databases and database management systems (DBMS)? What is a relational data base model? How are databases linked with GIS?

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CE 250 - Introduction to Surveying and G eographic I nformation S ystems

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  1. CE 250 - Introduction to SurveyingandGeographic Information Systems eLearning Version Donald J. Leone, Ph.D., P.E. Lecture 3

  2. 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?

  3. 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 tableform”, or “ A Collection of related data”

  4. Traditional Database Example

  5. Traditional Databases Some Problems • Duplication of Data • High Maintenance Costs • Data Sharing Difficulties • Lack of Security and Standards

  6. 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”

  7. Database Approach Database Data Database Management System DBMS Hotel Booking Ski School Booking Travel Arrangements Application

  8. Database Management SystemsFunctions • File Handling/management • Adding/deleting/updating records • Extraction of data (sorting, querying) • Maintenance (security, backup) • Application building

  9. Data Base Table

  10. Separate Data Tables – A Relational Database Zone Code PIN Ownername PIN Owner name Zone Code

  11. Creating a New Table JOIN Key Field

  12. Joined Table

  13. 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”

  14. Parcel Table “Which Parcels (PINS) have 2 or more acres?”

  15. Create a New Table Using SQL Query: “Acres” =>2.0 Result:

  16. Creating a Database • Data Investigation – Fact finding. • Data Modeling – Relationships between entities and attributes – Define Tables. • Database Design – Fit data modeling to software at hand. • Database Implementation – Filling in the actual data.

  17. Data ModelingEntity Attribute Modeling (EAM) • Identification of Entities • Identification of the Relationship between entities (1:1, 1:M, M:1, M:N) • Identification of the Attributes of the entities • Development of the Tables

  18. EAM for Ski Resort • Entitles – Hotels, Travel Companies, Ski Schools, Visitors • Relationships • Many visitors stayat One hotel (M:1) • One Travel Co, organizes for Many visitors (1:M) c)One Ski School teachesMany visitors (1:M) d)Different Travel Co.s may useDifferent Ski Schools (M:N)

  19. EAM Diagram N d b c • a) Many visitors stayat One hotel (M:1) • b)One Travel Co, organizes for Many visitors • (1:M) • c)One Ski School teachesMany visitors (1:M) • d)Different Travel Co.s may use • Different Ski Schools (M:N) a

  20. 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)

  21. Ski Resort Tables

  22. Linking Spatial and Attribute Data

  23. Database Applications Single User/PC Simple Software Large Computers Control Access Manage Data Security Different Sites Large Corporate Databases

  24. 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.

  25. Break!

  26. Getting the Data Into The ComputerData Input (Encoding) and Editing ANALOGDIGITAL • What is data encoding? • How are paper mapsdigitized? • How are paper mapsscanned? • Methods of Data Editing and Conversion

  27. Digital Data Soft Ideas Tabular Data Maps Satellite Data Scanning Digitizing Data Transfer Key Coding Data Encoding Methods Data Capture Editing/Cleaning Re-Projection Data Editing Generalization Edge Matching and Rubber Sheeting Layering Database Integrated GIS

  28. Data Encoding MethodsDigitizing • Tracing over a map with a cursor. • Mechanical Device with a Human Operator. • Most errors operator induced. • Produces A Vector Map.

  29. Data Encoding MethodsScanning 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.

  30. University of Hartford Aerial Photo Sports Center HJG Center UT Hall Ground Truthing Points

  31. Scanning Original Paper Map Scanned Image

  32. Data Encoding MethodsElectronic Data Transfer • What data exist? • How much they cost? • What format will it be in? Pay off – Considerable time and effort saved!

  33. Data Editing MethodsDetecting and Correcting Errors • Missing or Duplicate Features • Mislocated Features • Missing or Duplicated Labels • Unwanted Results of Digitizing or Scanning • Noise

  34. Errors in Vector Data

  35. Errors in Raster Data Noise Original “noisy” data 3 x 3 Mean Filter 9 x 9 Mean Filter

  36. Producing a Common Reference • Re-Projection • Transformation • Generalization

  37. Producing a Common Reference Re-Projection All data needs to be referenced to the same projection.

  38. Trying to Overlay Different Projections Cylindrical Conic

  39. Producing a Common Reference Re-Projection All data needs to be referenced to the same projection. Transformation All data needs to have the same origin.

  40. Producing a Common Reference Re-Projection All data needs to be referenced to the same projection. Transformation All data needs to have the same origin. Generalization All data needs to be set to the same scale.

  41. Remaining Problems After Re-Projection, Transformation, and Generalization Edge Matching

  42. Remaining Problems After Re-Projection, Transformation, and Generalization Rubber Sheeting

  43. An Integrated DatabaseSki Resort Example

  44. An Integrated DatabaseSki Valley Example

  45. 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?

  46. What’s Next • Up to now – Data Formation • Data Analysis – Decision Making

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