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GIS & Raster


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GIS & Raster

  1. 1. Presented By : <br /> Mohamed El-Serngawy<br />Computer Graphics and GIS<br />
  2. 2. Agenda<br />What is GIS? <br />Raster Data Format<br />Spatial Analyst <br />
  3. 3. What’s GIS?<br />Automated system for the capture, storage, retrieval, analysis and display of spatial data<br />Linking tabular data with its real location<br />Maps<br />Data<br />Analysis<br />
  4. 4. GIS representing real world data<br />
  5. 5. Abstracting Real World Objects into Layers<br />Buildings<br />Administrative Boundaries<br />Roads<br />Utilities<br />Land Use<br />Soil<br />
  6. 6. GIS Data<br />Data Types:<br />Spatial Data :<br />The kind of positional data that is related to earth’s surface <br />Attribute Data:<br />All information that are related to certain geographic feature<br />
  7. 7. GIS Data is intelligent<br />
  8. 8. Data Storage<br />
  9. 9. What is raster data?<br />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. <br />Datastoredin a rasterformatrepresentsreal-worldphenomena, such as <br />Thematicdata (also known as discrete), representing features such as land-use or soils data <br />Continuousdata, representing phenomena such as temperature, elevation, or spectral data such as satellite images and aerial photographs <br />Pictures, such as scanned maps or drawings and building photographs <br />General characteristics of raster data<br />In raster datasets, eachcell (which is also known as a pixel) has a value<br />Eachcell consists of the samewidth and height and is an equal portion of the entire surface represented by the raster..<br />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.<br />
  10. 10. Cont. What is raster data?<br />Cellvaluescan be either positiveornegative, integer, or floating point. <br />Integervalues are best used to representcategorical (discrete) data, and floating-point values to representcontinuous surfaces.<br /><ul><li>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. </li></li></ul><li>Spatial Analyst<br />Spatial Analyst is a set of tools implement graphic based algorithm to perform cell-based (raster) analysis <br />Example :<br /> 1-Euclidean distance <br /> 2-Point Density<br />
  11. 11. 1-Euclidean distance<br />The Euclidean distance output raster contains the measured distance from every cell to the nearest source<br />
  12. 12. 2-Point Density<br />Calculates a magnitude per unit area from point features that fall within a neighborhood around each cell<br />