M ETHODS OF REPRESENTING GEOGRAPHIC SPACE Raster Model Vector Model

M AP AS AN A BSTRACTION OF SPACE : Spatial features can be represented as points, lines and area(polygons). Some objects are selected for inclusion and another not spatial feature and it have attributes as 1- simplified 2-aggregated 3- classified. When the geographies want to enter the data to GIS, they have some decision need to made based upon to can entered it to computer.

T HE DEFINITION : Raster Models : It is that features made of cells and each cells related with another cells. Vector Models: It is that features included points, lines and polygons and their data is spaghetti.

V ECTOR M ODELS It is represent by (x, y) coordinates. Vector model take less storage. Example for vector model is digitization. We take long time when make vector model.

R ASTER MODELS It is represent by (pixel or cell) It is take more storage. Example for raster model is scanning. We take short time when make Raster model.

G EOGRAPHIC R EPRESENTATIONS CELLS: a representation of geographic data on rows and columns. PIXELS: a group of points with a color value but no data related to others

R ASTER AND VECTOR REPRESENTATION Vector representation Raster representation

C ONTINUE

R ASTER D ATA : A DVANTAGES AND D ISADVANTAGES DisadvantagesAdvantages The cell size determines the resolution at which the data is represented Due to the nature of the data storage technique data analysis is usually easy to program Processing of associated attribute data may be cumbersome The inherent nature of raster maps Raster maps normally reflect only one attribute for an area Discrete data most input data is in vector form, data must undergo vector-to-raster conversion Grid-cell systems are very compatible with raster-based output devices Most output maps from grid- cell systems compatible with digital satellite imagery

V ECTOR D ATA : A DVANTAGES AND D ISADVANTAGES DisadvantagesAdvantages The location of each vertex needs to be stored Data can be represented at its original resolution without generalization. For effective analysis, vector data must be converted into a topological structure Graphic output is usually more accurate Topology is staticAccurate geographic location of data is maintained. Algorithms for manipulative and analysis functions are complex Because it recognizes entities, model allows for efficient encoding of topology Continuous data, such as elevation data, is not effectively represented in vector form.

G RID DATA ( CELLS )

S ATELLITE IMAGE ( PIXELS )

V ECTOR V S. R ASTER RasterVector Want more spaceWant little spaceStorage space difficulteasyTopology Grides not very aesthetic Arces more aesthetically pleasing Aesthetic More simpleMore complexData structures limitedbetterGeographic specificity