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GIS & Raster
 

GIS & Raster

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    GIS & Raster GIS & Raster Presentation Transcript

    • Presented By :
      Mohamed El-Serngawy
      Computer Graphics and GIS
    • Agenda
      What is GIS?
      Raster Data Format
      Spatial Analyst
    • What’s GIS?
      Automated system for the capture, storage, retrieval, analysis and display of spatial data
      Linking tabular data with its real location
      Maps
      Data
      Analysis
    • GIS representing real world data
    • Abstracting Real World Objects into Layers
      Buildings
      Administrative Boundaries
      Roads
      Utilities
      Land Use
      Soil
    • GIS Data
      Data Types:
      Spatial Data :
      The kind of positional data that is related to earth’s surface
      Attribute Data:
      All information that are related to certain geographic feature
    • GIS Data is intelligent
    • Data Storage
    • What is raster data?
      In its simplest form, a rasterconsists of a matrixofcells (or pixels) organized into rows and columns (or a grid) where each cell contains a value representing information, such as temperature.
      Datastoredin a rasterformatrepresentsreal-worldphenomena, such as
      Thematicdata (also known as discrete), representing features such as land-use or soils data
      Continuousdata, representing phenomena such as temperature, elevation, or spectral data such as satellite images and aerial photographs
      Pictures, such as scanned maps or drawings and building photographs
      General characteristics of raster data
      In raster datasets, eachcell (which is also known as a pixel) has a value
      Eachcell consists of the samewidth and height and is an equal portion of the entire surface represented by the raster..
      The smaller the cellsize, the smoother or moredetailed the raster will be. However, the greater the number of cells, the longer it will take to process, and it will increase the demand for storagespace.
    • Cont. What is raster data?
      Cellvaluescan be either positiveornegative, integer, or floating point.
      Integervalues are best used to representcategorical (discrete) data, and floating-point values to representcontinuous surfaces.
      • The location of eachcell is defined by the row or column where it is located within the raster matrix. Essentially, the matrix is represented by a Cartesiancoordinatesystem, in which the rows of the matrix are parallel to the x-axis and the columns to the y-axis of the Cartesian plane. Row and column values begin with 0.
    • Spatial Analyst
      Spatial Analyst is a set of tools implement graphic based algorithm to perform cell-based (raster) analysis
      Example :
      1-Euclidean distance
      2-Point Density
    • 1-Euclidean distance
      The Euclidean distance output raster contains the measured distance from every cell to the nearest source
    • 2-Point Density
      Calculates a magnitude per unit area from point features that fall within a neighborhood around each cell