Más contenido relacionado


What is Geography Information Systems (GIS)

  1. GIS: Geography InformationGIS: Geography Information SystemsSystems
  2. What is GIS? a computer-based information system used to:a computer-based information system used to: What is GISWhat is GIS capture,capture, manage,manage, update,update, analyze,analyze, display, anddisplay, and output spatial data and informationoutput spatial data and information to be used in a decision making contextto be used in a decision making context GIS (Geographical Information System is:GIS (Geographical Information System is:
  3. What is GIS? Components of a GISComponents of a GIS HardwareHardware SoftwareSoftware DataData PeoplePeople ApplicationsApplications GIS
  4. What is GIS? Geography Brings Data TogetherGeography Brings Data Together Multiple Data Layers Geographically Referenced Common Coordinate System Provides basis for: • Data Integration • Systematic Analysis • Customized Maps
  5. What is GIS? GIS Data Model A layer-cake of information
  6. What is GIS? The GIS Data Model:The GIS Data Model: ImplementationImplementation Geographic Integration of InformationGeographic Integration of Information Digital Orthophoto Streets Hydrography Parcels Buildings Zoning Utilities Administrative Boundaries • Data is organized by layers, coverages or themes (synonomous concepts), with each layer representing a common feature. • Layers are integrated using explicit location on the earth’s surface, thus geographic location is the organizing principal.
  7. What is GIS? GIS Integrates Data & ApplicationsGIS Integrates Data & Applications Human Services Town Clerk Senior Center Parks & Recreation Town Manager Finance Health Building Police Engineering Assessor Planning Public Works Fire Department
  8. What is GIS? A GIS Manages Two Types of DataA GIS Manages Two Types of Data Attribute Data (what) information that defines and describes each feature Spatial Data (where) cartographic features points, lines & polygons
  9. What is GIS? Spatial and Attribute DataSpatial and Attribute Data • Spatial data (where) – specifies location – stored in a shape file, geodatabase or similar geographic file • Attribute (descriptive) data (what, how much, when) – specifies characteristics at that location, natural or human-created – stored in a data base table – It is information that is additional to geographical location. (Spatial Data) E.g. Names, descriptions, labels, statistics, measurements, categories, codes, dates, symbology. GIS systems traditionally maintain spatial and attribute data separately, then “join” them for display or analysis for example, in ArcView, the Attributes of … table is used to link a shapefile (spatial structure) with a data base table containing attribute information in order to display the attribute data spatially on a map
  10. What is GIS? The GIS Model: LayeringThe GIS Model: Layering roads hydrology topography Here we have three layers or themes: --roads, --hydrology (water), --topography (land elevation) They can be related because precise geographic coordinates are recorded for each theme. longitude latitude longitude longitude latitude latitude Layers are comprised of two data types •Spatial data which describes location (where) •Attribute data specifing what, how much,when Layers may be represented in two ways: •in vector format as points and lines •in raster(or image) format as pixels All geographic data has 4 properties: projection, scale, accuracy and resolution
  11. What is GIS? Layers are represented inLayers are represented in RasterRaster or Vectoror Vector formatformat Raster Model • area is covered by grid with (usually) equal-sized, square cells • attributes are recorded by assigning each cell a single value based on the majority feature (attribute) in the cell, such as land use type. • Image data is a special case of raster data in which the “attribute” is a reflectance value from the geomagnetic spectrum – cells in image data often called pixels (picture elements) • Vector Model The fundamental concept of vector GIS is that all geographic features in the real work can be represented either as: • points or dots (nodes): trees, poles, fire plugs, airports, cities • lines (arcs): streams, streets, sewers, • areas (polygons): land parcels, cities, counties, forest, rock type Because representation depends on shape, ArcView refers to files containing vector data as shapefiles
  12. What is GIS? 0 1 2 3 4 5 6 7 8 9 0 R T 1 R T 2 H R 3 R 4 R R 5 R 6 R T T H 7 R T T 8 R 9 R Real World Vector Representation Raster Representation Concept of Vector and Raster line polygon point
  13. What is GIS? Street Network layer: lines Land Parcels layer: polygons Raster (image) Layer Digital Ortho Photograph Layer: Digital Ortho photo: combines the visual properties of a photograph with the positional accuracy of a map, in computer readable form. Vector Layers Layers Projection: State Plane, North Central Texas Zone, NAD 83 Resolution: 0.5 meters Accuracy: 1.0 meters 0 1500 3000 Feet
  14. What is GIS? Visualizations - Layer ControlVisualizations - Layer Control
  15. What is GIS? Different Ways to View DataDifferent Ways to View Data
  16. What is GIS? GIS Applications – What GIS is used forGIS Applications – What GIS is used for • Property assessment • Wetlands regulation • Emergency response • Infrastructure management • School redistricting • Law enforcement • Open space planning • Greenway planning • Access to health services • Forest management • Homeland security • Transportation planning • Site suitability / selection • Build-out analysis • Search and rescue • Plans of C & D • Map design & production • Watershed protection • Permit review • E-911 • Farmland protection • Aquifer protection • Archaeological research • Economic development
  17. What is GIS? Examples of Applied GISExamples of Applied GIS • Urban Planning, Management & Policy – Zoning, subdivision planning – Land acquisition – Economic development – Code enforcement – Housing renovation programs – Emergency response – Crime analysis – Tax assessment • Environmental Sciences – Monitoring environmental risk – Modeling stormwater runoff – Management of watersheds, floodplains, wetlands, forests, aquifers – Environmental Impact Analysis – Hazardous or toxic facility siting – Groundwater modeling and contamination tracking • Political Science – Redistricting – Analysis of election results – Predictive modeling • Civil Engineering/Utility – Locating underground facilities – Designing alignment for freeways, transit – Coordination of infrastructure maintenance • Business – Demographic Analysis – Market Penetration/ Share Analysis – Site Selection • Education Administration – Attendance Area Maintenance – Enrollment Projections – School Bus Routing • Real Estate – Neighborhood land prices – Traffic Impact Analysis – Determination of Highest and Best Use • Health Care – Epidemiology – Needs Analysis – Service Inventory
  18. What is GIS? Provide examples of data pre-processing. (1) Georeferencing– The process of giving images in your GIS real-world coordinates. (2) Digitising— features on paper-based maps are traced using a mouse type device called a cursor (it is stored in vector format) (3) Scanning— a scanner converts hardcopy maps and documents into digital images. (4) Features and Attribute tables— Attributes are attached to the vector feature in the GIS by using a data table. The columns are the different kinds of attributes, the rows are the individual vector features that have been digitized.
  19. What is GIS? Name and explain 4 steps to follow when creating a GIS project. 1)Data collection. The process of finding data. 2) Data pre-processing. Data is made user-friendly by undergoing distortion adjustments and geometric registration. (See slide on data pre-processing). 3) Data Management. Storing and updating large amounts of data and making it easier for users to find the data. 4) Data Analysis and Manipulation. Data can be analyzed and change into information. ApplicationsApplications
  20. What is GIS? What is a GIS project? (Provide some examples of GIS projects). A Gis project is one that uses spatial / geographical data to answer a particular question: 1) Agriculture: How can food production be improved? 2) Emergency: What is the fastest route to the hospital? 3) Retail: Where is the best to build a new shopping centre? 4) Marketing: Where do the people live that I want to sell to?
  21. What is GIS? GIS ProjectsGIS Projects • Locating a Day-care – intro to GIS capabilities – illustration of a major application: site selection • Texas Demographic growth – manipulation of data and mapping principles – another major application: analysis of spatial patterns with polygon data • Geocoding Housing Sales, or Analyzing Earthquake Locations – techniques and data requirements for geocoding and point patterns – another application: geocoding/address matching • Creating a Census Tract layer, or a Geological Map – editing and creating topologically consistent data – how new data layers can be created • Pipeline Routing – data selection, buffering and spatial analysis – another major application: corridor studies
  22. What is GIS? Perform Spatial AnalysesPerform Spatial Analyses Find Buildings Within 250m of streams
  23. What is GIS? Public Utility ApplicationsPublic Utility Applications Select Suitable Site for Water Company Well . Water Company Service Area Only within undeveloped land areas Within undeveloped land area, only outside buffer of polluted streams and known point sources of pollution. Only surface geology that shows greatest potential for water production
  24. What is GIS? How does GISHow does GIS data get stored?data get stored?Data Decisions Science M anagem ent Many GIS applications store digital data in a database. GIS data is stored in a number of file formats, but the shape file is the most common. It consists of at least three different files that work together to store digital vector data as shown in the table below. A database is a storage system linked to tables.
  25. What is GIS? Sources of data used in a GIS 1)Primary data: Data collected in the field by physically measuring, observing and interpreting objects e.g. GPS measurements, scanned in maps. 2) Secondary data: Data that already exists in one format or another. It is data that can be reused e.g. maps, databases, images and aerial photographs. Name two ways in which primary data is collected. 1) Ground-based surveys. E.g tachymetry 2) GPS
  26. What is GIS? What is metadata? Metadata is data about data. Provide some examples of metadata. Names of people responsible for creating the data. A textual description of the content of the data. Dates and times of when the data was produced. Map projection / spatial resolution used.
  27. What is GIS? GIS aspects that need agreement on global standardisation include: •The global map projections used. •Methods of Georeferencing. •Geographical names. •Units of measurement used. •Methods of processing digital data. Data Standardisation Growing of GIS has resulted in intense efforts at data standardisation to establish structures and methods for the interchange of spatial data.
  28. What is GIS? Data sharing offers several advantages: •It avoids expensive repetition of data acquisition (e.g. sensors in orbit). •It makes a wide range of data available to people all over the world. •It reduces workload and cost Data Sharing Data sharing between organisations with different GIS could only be achieved by data converters, transfer standards and open file formats.
  29. What is GIS? Data is protected in several ways: •Data must be secure from loss or computer failure. •Data must be secure from fraud. •Some files (databases) of municipalities and the government must be kept secret. •The police, fire brigade and ambulance have data files that would be of interest to criminals / terrorists and have to be protected. Data Security Data and information can sometimes be highly sensitive, either for commercial or personal confidentiality or national security. To ensure data security the data can only be accessed with authorisation codes.
  30. What is GIS? Data Manipulation Data needed for GIS comes from many different sources. They will need to be transformed or manipulated in some way to make them compatible with the GIS system Examples of Data Manipulation:Examples of Data Manipulation: Creation of buffers, creation of models, integration of data layers, conversion of data from raster and vector formats, interpolation between points .
  31. What is GIS? To correct distortionsTo correct distortions Why is it necessary to manipulateWhy is it necessary to manipulate data in a database?data in a database? To sharpen definitionsTo sharpen definitions To ensure colour consistencyTo ensure colour consistency To ensure correct latitude andTo ensure correct latitude and longitudelongitude Linked database tableLinked database table Spatial dataSpatial data
  32. What is GIS? Data Integration What are the problems of integrating data? Maps have different scales Maps have different projections Maps have different georeferences What is the importance of integrating data? A summary of integrated data is produced and is easier to understand Data integration involves the combination of two or more layers in order to create a new one.
  33. What is GIS? Data Querying You can begin to ask questions: GIS allows querying in order to answer Geographical questions and help solve complex problems. It’s displayed graphically! The vegetation layer is compared with the soil data layer. The shrubs and sand areas are overlaid and only the areas adhering to the query are shown.
  34. What is GIS? Answers to Simple QuestionsAnswers to Simple Questions ? Visualize spatial relationships Answer questions about what “it” is Answer questions about where things are Ad hoc queries are one of the most important and basic of all GIS functions Ad hoc queries are one of the most important and basic of all GIS functions
  35. What is GIS? • That were sold in the past 3 years • For more than $200,000 Queries - Class of FeaturesQueries - Class of Features • Select all parcels in a subdivision
  36. What is GIS? A buffer refers to an area around a point, line or polygon. You can demarcate a buffer area of for example 3 km around a place on the map. EXAMPLES OF BUFFERING: What is the total number of customers within 10 km of this shopping mall? Which areas will be affected by a 1m rise in sea level? Which residential areas will be affected by a nuclear fallout affecting a radius of 60 km from the nuclear power station? MapInfoMapInfo Buffering
  37. What is GIS? Statistical Analysis Information such as: Statistical Analysis is used to investigate GIS data and assist in the identification of additional information. Spatial patterns Spatial trends Climatic averages e.g. temperature and rainfall Which layers would GIS researches use to determine the risk of a landslide: Altitude Slope angle Rock type Land cover Slope exposure Distance from rivers Profile curvature Surface curvature Distance from the road Drainage Basin
  38. What is GIS? What remote sensing is used for: Remote sensing is obtaining data from a distance without touching the object. Instruments used to collect the information are the camera, radar, sonar, thermal and electro-optical sensors. Remote sensing is used to study weather patterns, climate change, urban change, the atmosphere, landscapes, ecosystems, human impact on the environment, the oceans and hydrology.
  39. What is GIS? Spatial ResolutionSpatial Resolution • Satellite images are captured in digital format. • They consist of a very fine grid of squares called ‘picture cells’ or ‘pixels’. (Raster data) • Coarse (low) resolution if the pixel covers a large area on the ground • Fine (high) resolution covers a smaller area on the ground. Spatial Resolution refers to the size of an object that can be recorded; the most usual method is the pixel size.
  40. What is GIS? Spectral ResolutionSpectral Resolution Spectral resolution refers to the width of the wavelength intervals that are being measured in the electromagnetic spectrum. Remote sensors can collect data in the visible part of the spectrum (to provide images such as aerial photographs). Other sensors may collect data in the invisible sectors like infrared (seen below) and ultraviolet.
  41. What is GIS? Vertical Aerial Photograph – Taken from above, camera is pointing vertically downwards. High Oblique Aerial Photograph – Horizon is visible. Camera is tilted at 68 degrees. Low Oblique Aerial Photograph – Horizon is not visible. Camera is tilted at 30 degrees.

Notas del editor

  1. A GIS is not just hardware and specialized software; it also includes data, applications, people and procedures for its use and maintenance. Applications are perhaps the most important yet overlooked component of a GIS. Applications are what a GIS will be used for. They determine many of the other elements of a system; for example, what data will be necessary, how it will be processed, who will access the data and what products or information the system will produce. Having a clear understanding of applications and system use is a critical first step to system design and implementation.
  2. The purpose of this slide is allow the presenter to list the major components of a GIS and to discuss how they are integrated into a SYSTEM. Hardware and software range from stand-alone desktop systems to complex enterprise-wide networks. Data include existing public domain data sets, an organization’s own data that may be created in-house or through arrangements with another organization or vendor. Note that data are expensive, both to create and to maintain. Higher accuracy data cost orders of magnitude more than less accurate data. Accuracy and cost should match the requirements of the applications. Applications and procedures define the uses of the GIS and the standardized methods, if appropriate, that will insure consistent high quality output and analyses. The applications determine data needs. Trained and knowledgeable people to operate and maintain a system are essential. They can be expensive and they need continued training.
  3. Note that GIS data consist of cartographic features: Pointswells, utility poles, manholes Linesroad centerlines, small streams, trails Polygonsparcels, wetlands, building footprints, watersheds AND Attribute data that describe each feature AND that features and attributes are linked This permits accessing and analyzing GIS data either based on where it is or what it is; on in some cases based on a combination of where and what.
  4. This example retrieves data for a single feature. Simply click on the polygon and its database record will be displayed. Ad hoc queries such as this are a prime use of GIS.