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
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