Gis

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Gis

  1. 1. GEOGRAPHICAL INFORMATION SYSTEM
  2. 2. An organized collection of computer hardware, software, Geographical data and personnel designed to efficiently capture, store, update, manipulate, analyze & display all forms of Geographically referenced information GEOGRAPHIC INFORMATION SYSTEM
  3. 3. What is a GIS? Geographic Information System • “There are as many definitions as there are disciplines using a GIS” (Huxhold, 1991)
  4. 4. WHAT IS A GIS ? GEOGRAPHIC implies that locations of the data items are known, or can be calculated, in terms of Geographic coordinates (Latitude, Longitude) INFORMATION implies that the data in a GIS are organized to yield useful knowledge, often as coloured maps and images, but also as statistical graphics, tables, and various on-screen responses to interactive queries. SYSTEM implies that a GIS is made up from several inter- related and linked components with different functions. Thus, GIS have functional capabilities for data capture, input, manipulation, transformation, visualization, combinations, query, analysis, modelling and output.
  5. 5. What is a GIS? A GIS is a database management system for spatially distributed features and the associated attributes. • Spatial data capture • Management • Analysis • Display • Decision making • Research
  6. 6. GEOSPATIAL DATA USERS COMPUTER SYSTEM KEY COMPONENTS OF GIS Hardware&Software Capture, Storage, processing Analysis, Display etc., Maps, Aerial photographs, Satellite Images, Statistic Tables etc, Design of Standards, Updating, Analysis and Implementations
  7. 7. *COMPUTERISED CARTOGRAPHY -- performing cartographic functions by means computer hardware and software *CARTOGRAPHY -- art and science of map making A map represents geographic features or other spatial phenomena by graphically conveying information about locations and attributes *MAP •Map(graphic) information * only graphic data is available and retrieval * networks are not defined. •Map publication * spatial relationship not defined Computer Assisted Mapping INTRODUCTION
  8. 8. PERSONNEL ROLE OF LOCATION - ORGANISATION VIEWERS USERS DOERS
  9. 9. BASIC FUNCTIONS OF GIS WHAT IS IT….? (LOCATIONS) JFM AREA (X,Y) WHERE IS IT ….? (CONDITIONS) WITHIN THE FOREST BLOCK HOW HAS IT CHANGED …? (TRENDS) IMPROVEMENT IN FOREST GROWTH IN FIVE YEARS WHICH DATAARE RELATED ….? (PATTERNS) NEAREST JFM VILLAGE WHAT IF….? (MODELS) FINDING SOLUTIONS TO THE FORTH QUESTIONS
  10. 10. DATA ATTRIBUTE DATA SPATIAL DATA
  11. 11. SPATIAL DATA Raster Vector DATA MODELAND STRUCTURE RASTER MODEL VECTOR MODEL
  12. 12. ADVANTAGES OF VECTOR MODEL • PRECISE EXPRESSION • LESS DATA VOLUME • FULL TOPOLOGY • FAST RETRIEVAL • FAST CONVERSION ADVANTAGES OF RASTER MODEL • SIMPLE DATA STRUCTURE • EASY FOR OVERLAY AND MODELLING • SUITABLE FOR 3D DISPLAY • INTEGRATION OF IMAGE DATA • AUTOMATED DATA CAPTURE DISADVANTAGES OF VECTOR MODEL • COMPLICATED STRUCTURE • DIFFICULTY IN OVERLAY • DIFFICULTY IN UPDATING • EXPENSIVE DATA CAPTURE DISADVANTAGES OF RASTER MODEL • LARGE DATA VOLUME • LOW PRECISION • DIFFICULTY IN NETWORK ANAYLYSIS • SLOW CONVERSION
  13. 13. What Data is in Your GIS? • What features do you map? • What attributes do you need to collect data on? • What attribute values can you give the attribute?
  14. 14. Point Features Spatially distributed entities, activities or events • Points have a single geographic coordinate such as: – Tree – Traffic accident – Lamp post
  15. 15. Line Features Spatially distributed entities, activities or events • Lines (Arcs) are a series of geographic coordinates joined to form a line such as: – Road – Stream – Railway
  16. 16. Area Features Spatially distributed entities, activities or events • Areas (Polygons) are a series of geographic coordinates joined together to form a boundary such as: – Lake – Soil types
  17. 17. Automated Mapping/Facility Management Graphic files Non-graphic files 1 2 3 4 2. Dulapally beat Sift Dulapally Network defined by preserving intersection ID Number
  18. 18. Attribute data Attributes can be numeric or alfanumeric data that is assigned to a point, line or area spatial features Example Attributes… Stand ID, Compartment no,Vegetation type, Name of the Forest Block,Type of Road,VSS code etc.,
  19. 19. Data Capture Sources • Digitizing from paper maps • Scanning • Traditional surveying techniques • Paper records & field notes • Photogrammetry • Remote sensing • GPS
  20. 20. GIS Data Storage There are two main types of data in a GIS database • Cartographic - observations on spatially distributed features, activities, or events, which are definable as: – Points – Lines (Arcs) – Areas (Polygons)
  21. 21. GIS Data Storage • Non-Cartographic - descriptive information in a database about the cartographic features located on a map. – Attributes – Attribute Values
  22. 22. Attributes Description or characteristic of a feature • Possible attributes for the feature Tree – Height – Diameter – Species – Condition – Age
  23. 23. Attribute Values The value given to an attribute • Possible values for the attributes of a Tree feature – Height = 15m – Diameter = 0.75m – Species = Oak – Condition = Good – Age = 8 years
  24. 24. DATA STRUCTURES - POINT, LINE, POLYGON, THEME PERSONNEL - VIEWERS, USERS, DOERS ROLE OF LOCATION - ORGANISATION DATA COLLECTION - SOURCES OF DATA - CONVERSION TO DIGITAL FORMAT, PROCESSING,STORAGE, UPDATION ANALYSIS - OVERLAY, BUFFER, DISSOLVE, LINKING WITH RDBMS CODING - NEED FOR CODE - LOGISTICS IN CODING OUTPUTS - HARD COPIES, SOFTWARES, MODELS ADVANTAGES OF GIS
  25. 25. Type of Errors • Dangle Node • Undershoot • Overshoot • Missing Labels • Duplicate labels • Pseudo nodes • Unclosed polygon • Incorrect user ID to the features
  26. 26. Types of Attribute Values There are a number of different types of attribute values Feature Attribute Attribute Values Character Pole Pole ID ABC123 Numeric Pole Height 15m Menu Pole Condition Good Average Poor Date Pole Date User generated Auto generated Time Pole Time User generated Auto generated
  27. 27. BASIC FUNCTIONS OF GIS • DATA AQUISITION AND PREPROCESSING DIGITIZING EDITING TOPOLOGY BUILDING PROJECTION ATTRIBUTION
  28. 28. TOPOLOGY • Topology mathematical representation of geographic features(arcs, nodes, polygons and points) • When topology is built,it creates spatial relationship among the features • Topology can be very important for certain types of analysis.
  29. 29. TOPOLOGIC DATA ELEMENTS Node Line (Arc) Area(polygon) Nodes: defines beginning and end of the line Line: defines roads,utilities,boundaries,etc., Areas: administrative boundaries, forest block,JFM areas,lakes
  30. 30. LOGISTICS IN CODING CODING NEED FOR CODE JFM_CODECOMPT_CODEDDRB_CODE
  31. 31. PROJECTION GEOREFERENCING/GEOCODING SPATIAL DATA Transforming three-dimensional space onto a two-demensional map is called ‘projection’ or Projection is a mathematical expression which convert data from a geographical location(lat & long) on sphere or spheroid to a representative location on a flat surface. This much earth surface has to fit onto this much map surface Projection Plane *Conformal projections *Equal-area projections *Equidistant projections
  32. 32. WHY GIS ? • To inventory and monitor resources • To test the sensitivity of our analysis assumptions • To simulate potential impacts of management alternatives • To make the map the 2nd time, the 50th time, the 100th time...
  33. 33. Uses of a GIS • Mapping geographical characteristics for analysis • Modeling alternative processes for management plans • Managing a utility’s assets • Monitoring changes in environmental factors
  34. 34. Integration of Data GIS data • A GIS allows integration of data collected: – At different times – At different scales – Using various methods of capture
  35. 35. GIS Data Analysis • A GIS identifies relationships among features in the database • Provide answers to queries that are spatial (geographic)
  36. 36. THEMATIC OVERLAY 1. TOPOGRAPHY 2. BOUNDARIES 3. VEGETATION 4. ROADS 5. RIVERS 6. SOILS
  37. 37. Query and Analysis Data Query Output Veg_type - Area feature -Potential are available for jfm - 3 Village locations with density-type classes MT MISC Identify areas where density is lt 0.2 within 5km from the center of the village Density map 1-dense 2-open 3-scrub 4-blanks Report TEAK BAMBOO 4 32 3 1 2 1 4 Village Buffer 5km 1 2 3 4 5 6 3 4 5
  38. 38. DATABASE MANAGEMENT AND RETRIEVAL HIERARCHICAL MODELING NETWORK MODELING RELATIONAL MODELING ATTRIBUTE QUERRY DATABASE: COLLECTION OF INFORMATION ABOUT THINGS AND THEIR RELATIONSHIP TO EACH OTHER DBMS : A SET OF PROGRAMS THAT IS DESIGNED TO MANIPULATE MAINTAIN DATA IN A DATABSE
  39. 39. UNIVERSITY DEPARTMENT STUDENTS PROFESSORS REGISTRATION COURSES Hierarchical modeling M I II a cb d 1 3 122 43 4 fe gc 3 5 634 65 4 I II e g c d b a f 1 2 4 6 53 MAP M M I II a b c d e f g 1 2 3 4 5 6 Network linkages
  40. 40. ADVANTAGES OF GIS IN SIMPLE TERMS • Though collection of data is difficult once it is collected, it can be stored safely in digital form (in computer) forever without damage, which usually happens to our maps. • Once if a map is prepared accurately it can be printed in any scale without any redrawing. • Large scale maps at smaller units (Beats) level can be joined for creating maps at divisions or district level, very accurately within few minutes. • Changes can be incorporated very easily in computer and it doesn’t require any redrawing. • Same map can be generated even after 100s of years later. • New things can be known after overlay of different themes and a new types of maps can be generated. • Work can be done faster than manually. • The work of decision makers and end users will become easier.

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