1.Presented By :
Mohamed El-Serngawy
Computer Graphics and GIS

2. Agenda
What is GIS?
Raster Data Format
Spatial Analyst
3. Whats GIS?
Automated system for the capture, storage, retrieval, analysis and display of spatial data
Linking tabular data with its real location
Maps
Data
Analysis
4. GIS representing real world data
5. Abstracting Real World Objects into Layers
Buildings
Administrative Boundaries
Roads
Utilities
Land Use
Soil
6. GIS Data
Data Types:
Spatial Data :
The kind of positional data that is related to earths surface
Attribute Data:
All information that are related to certain geographic feature
7. GIS Data is intelligent
8. Data Storage
9. 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.
10. 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.