Pannasastra University of Cambodia

2/16/2016

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Exploring GIS data Geographic data models • ArcGIS stores and manages geographic data in a number of formats. • The three basic data models that ArcGIS uses are vector, raster, and TIN. • We can also import tabular data into a GIS.

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Mr.Meang Sotha and Mr.Sar Sovoeun

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Pannasastra University of Cambodia

2/16/2016

Exploring GIS data Vector models • points, lines, and polygons. •Points are pairs of x,y coordinates. •Lines are sets of coordinates that define a shape. •Polygons are sets of coordinates defining boundaries that enclose areas. 3

Exploring GIS data • Coordinates are most often pairs (x,y) or triplets (x,y,z, where z represents a value such as elevation). • The coordinate values depend on the geographic coordinate system the data is stored in. • ArcGIS stores vector data in feature classes and collections of topologically related feature classes. 4

Mr.Meang Sotha and Mr.Sar Sovoeun

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Pannasastra University of Cambodia

2/16/2016

Exploring GIS data • The attributes associated with the features are stored in data tables. • ArcGIS uses three different implementations of the vector model to represent feature data: coverages, shapefiles, and geodatabases.

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Exploring GIS data Raster models • In a raster model, the world is represented as a surface that is divided into a regular grid of cells. • The x,y coordinates of at least one corner of the raster are known, so it can be located in geographic space. 6

Mr.Meang Sotha and Mr.Sar Sovoeun

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Pannasastra University of Cambodia

2/16/2016

Exploring GIS data Raster models • Raster data includes images and grids. Images, such as an aerial photograph, a satellite image, or a scanned map.

scanned map

Aerial photograph

Satellite image

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Exploring GIS data Raster models • Grids can store continuous values, such as for an elevation surface. • They can also store categories, such as for a grid of vegetation types.

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Mr.Meang Sotha and Mr.Sar Sovoeun

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Pannasastra University of Cambodia

2/16/2016

Exploring GIS data Raster models • Grids storing categorical information can store Additional attributes about each category. TIN models • In a triangulated irregular network model, the world is represented as a network of linked triangles drawn between irregularly spaced points with x, y, and z values. 9

Exploring GIS data Format of Feature Data • ArcGIS supports both file-based feature models and database management system (DBMS) feature models. -The two file-based models are coverages and shapefiles. -The DBMS feature model supported by ArcGIS is the geodatabase data model. 10

Mr.Meang Sotha and Mr.Sar Sovoeun

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Pannasastra University of Cambodia

2/16/2016

Q/A Thank you for attendant 11

Mr.Meang Sotha and Mr.Sar Sovoeun

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