1 / 56

INTRODUCTION TO GEOGRAPHIC INFORMATION SYSTEMS

INTRODUCTION TO GEOGRAPHIC INFORMATION SYSTEMS. GOALS. Answer the question: “What is a GIS?” Learn some of the basic terminology used in a GIS Become familiar with the general operations and applications of a GIS See some of the analyses performed in a GIS. Information Systems.

selah
Download Presentation

INTRODUCTION TO GEOGRAPHIC INFORMATION SYSTEMS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. INTRODUCTION TO GEOGRAPHIC INFORMATION SYSTEMS

  2. GOALS • Answer the question: “What is a GIS?” • Learn some of the basic terminology used in a GIS • Become familiar with the general operations and applications of a GIS • See some of the analyses performed in a GIS

  3. Information Systems

  4. Data vs. Information • Data, by itself, differs from information • Data is of little use unless it is transformed into information • Information is an answer to a question based on raw data • We transform data into information through the use of an Information System

  5. Information System

  6. What is a GIS? • More than just an electronic map maker • More than a digital database • More than just a software package

  7. GIS--What is it?No easy answer! • Geographic/Geospatial Information • information about places on the earth’s surface • knowledge about “what is where when” • Geographic/geospatial: synonymous • GIS--what’s in the S? • Systems: the technology • Science: the concepts and theory • Studies: the societal context

  8. What is a GIS? • A GIS is a computer system capable of assembling, storing, manipulating/ analyzing, and displaying geographically referenced information (spatial), i.e. data identified according to their locations. • A decision support system involving the integration of spatially reference data in a problem solving environment. • A GIS also includes operating personnel and the data that go into the system.

  9. Components of a GIS

  10. Geographic Information System: intuitive description • A map with a database behind it. • A virtual representation of the real world and its infrastructure. • A consistent “as-built” of the real world, natural and manmade Which is • queried to support on-going operations • summarized to support strategic decision making and policy formulation • analyzed to support scientific inquiry

  11. GIS System Architecture and Components Data Input Query Input Geographic Database Transformation and Analysis Output: Display and Reporting

  12. GIS Knowledge Base for GIS Computer Science: graphics visualization database system administration security Application Area: public admin. planning geology mineral exploration forestry site selection marketing civil engineering criminal justice surveying Geography and related: cartography geodesy photogrammetry landforms spatial statistics. The convergence of technological fields and traditional disciplines.

  13. Streets People Air Photos Software Buildings Procedures Hardware Components of a GIS GIS

  14. Sources of Input Data • Global Positioning System (gps) • a system of earth-orbiting satellites which can provide precise (100 meter to sub-cm.) location on the earth’s surface (in lat/long coordinates or equiv.) • Remote Sensing • Use of satellites or aircrafts to capture information about the earth’s surface • Digital images a key product (map accurate digital photos)

  15. Properties of Real World Geographic Information • Location • Attributes • Spatial Relationships

  16. Geographic Objects • So the question arises: “How do we represent an object in space with a computer?” • An object is any geographically referenced entity • Lake, river, road, country, sampling site, etc.

  17. Outline for The Remaining • Three steps are involved in order to go from the real world geographic object to geographic object on the computer • Representations of Geographic Reality • Linking Attributes to Geographic Representation • Spatial Relationships between Geographic Representations

  18. 1. Representations of Geographic Reality: The Data Model Approach

  19. Data Models • Allows the geographic features in real world locations to be digitally represented and stored in a database so that they can be abstractly presented in map (analog) form, and can also be worked with and manipulated to address some problem Two common methods are used: • Vector data model • Raster data model

  20. Vector Data Model • Abstract spatial features • Point • Line • Area (polygon) • Record coordinates • Good for representing clearly defined objects • Spatial relationships can be defined

  21. Point Line LineString Or MultiLine Area or Polygon

  22. roads hydrology topography The Vector GIS Model: examples Here we have three layers orthemes: --roads, --hydrology (water), --topography (land elevation) They can be related because precise geographic coordinates are recorded for each theme. latitude longitude latitude • Layers are comprised of two data types • Spatial datawhich describes location (where) • Attribute dataspecifying what, how much, when • All geographic data has 4 properties: • projection, scale, accuracy and resolution longitude latitude longitude

  23. Raster Data Model • Regular grid of cells • Each cell represents an area on the ground • Spatial resolution • Value assigned to cell represents attribute • Land cover • Elevation • Satellite images • Good for representing continuously changing attributes

  24. Concept of Vector and Raster Real World Raster Representation Vector Representation point line polygon

  25. Each cell in the raster data set represent average color in 30mX30m area

  26. 0 3000 Feet 1500 Layers Vector Layers Street Network layer: lines Land Parcels layer: polygons Raster (image) Layer Projection: State Plane, North Central Texas Zone, NAD 83 Resolution: 0.5 meters Accuracy: 1.0 meters Scale: see scale bar

  27. Overlay based on Common Geographic Location

  28. Location • Absolute locations • Described by coordinate system • geographic • projected • Relative locations • Described through a relationship between objects.

  29. a. Geographic Coordinate Systems • Reference system for curved surface of earth • Network of intersecting lines • Longitude • Latitude • The starting point is defined at the intersection of equator and primary meridian.

  30. b. Projected Coordinate System • Reference system for features on a flat (projected) surface • Cartesian coordinate system with designated origin • Many different projected coordinate systems • Ex. UTM

  31. 1 Cylindrical • 2 Conical Map Projections 1 • Projection of round earth onto flat surface 3 • 3 Planar • Common • 1 Transverse Mercator • 2 Albers • 3 Robinson 2

  32. 2. Linking Attributes to Geographic Representation

  33. Attributes • Non-spatial data associated with objects • Information about the objects in our GIS • Land cover • Stream name • Flow rate • Land owner • Address • Stored in tables that are linked with objects • Polygon Attribute Table, Arc Attribute table, Point Attribute Table

  34. GIS as a Database • Links attribute data to spatial data • Spatially relates different objects • Topology • Allows for spatial and attribute data queries and analysis

  35. 3. Spatial Relationships between Geographic Representations

  36. Spatial Relationships • Geometric characteristics of individual objects • Length, area, perimeter, shape • Spatial relationships between 2 or more objects • Distance, direction, topology • Spatial distribution of objects • How objects are distributed in space

  37. Topology • Topology is defined as the “spatial relationships between adjacent or neighboring features.”

  38. Fundamental GIS Operations

  39. Fundamental GIS Operations • Capture • Store • Edit • Analysis • Display • Output

  40. i. Capturing Data • Databases • GPS • Remote Sensing • Sensors • Others

  41. ii. Data Storage • Through database management system • Links attribute to spatial information

  42. iii. Data Editing • Updating or correcting features • shapes and attributes

  43. iv. GIS Analysis • “Visualizing and combining geographic data to derive new information” • Overlay maps, plotting population on a map etc. • Queries • attribute, location • Geoprocessing • Analysis of spatial relationships between objects in a layer or objects in multiple layers • create new data sets

  44. Geoprocessing • Any GIS operation that creates new data • Simple • Copy one data set and paste it somewhere else • Advanced • Multiple operations on multiple data sets to create new, unique features

  45. Data extraction creating a subset of features from one data set based on the geographic extent of another Overlays combination of two or more data sets to create new data set Advanced Geoprocessing • Proximity • finding areas that are near features

  46. Data Query • Queries are used to pull information out of a GIS • You can think of a query as a question posed to the GIS • Replies with both spatial and attribute information

More Related