Introduction to GIS

GIS/CAD5

CAD – Computer Aided DesignGIS – Geographic Information

System

CAD – drawing, editing, construction, project

visualisation - 2D and 3D

GIS - mostly 2D - mapping, information collection,

spatial analyses, interpretation

GIS - essential terms

Map – consists of layers and symbolisation

Layer – set of single-type information- parcels, streets, buildings, contour-lines, … also called as feature class

Feature – a single map object- building, pond, …

Attribute – a single characteristics of feature- height, area, type, …

Map – consists of layers

Layers

geometry Vector Raster

Point

Line

Polygon

• Layers in GIS usually can not contain more than one geometry type• One GIS layer normally corresponds to one file

Feature – single object of a layerGIS feature consists of 2 parts:

• Layer is represented as TABLE• Features is represented as ROW of the table

Geometry

Attributes

Attributes – characteristics of the features

•Attributes are represented as COLUMNS of the table

Geometry

Attributes

Understanding to Drawings and Layers

1. CADDrawing = File

consists of layersdata and other information at

one file

Drawing (file)

Layer

Layer

Layer

Drawing (file)

Layer

Layer

Layer

Reference layer

Understanding to Drawings and Layers

2. GISLayer = FileProject = (map) File

consists of reference to layersinformation on selection and

symbolisationlayout graphics (legend, titles,

etc.)

Layer (file)

Project (file)

Layer (file) Layer (file)

Project (file) Project (file)

GIS data formats

Note: SW GIS normally can read CAD files!

ESRI Shapefile (SHP) – GIS commercial standardGML – XML based standard (not much supported)

ESRI Geodatabase (GDB, MDB)

TIN (vector surface)GRID (raster data)GeoTIFF, JPG, PNG, …

Rasters must have coordinate system reference!

Layers – data sources and storage

• Files– GIS formats (shapefile, geodatabase file,

rasters)– CAD formats (DXF, DWG, DGN)

• On-line WWW services– Raster services (WMS)– Vector services (WFS)

• Database tables (Oracle, PostGIS, …)

Useful links:

http://support.esri.com – ESRI vendorhttp://resources.esri.com – ESRI

vendor

http://geoportal.gov.cz – Czech Geoportal

http://geoportalpraha.cz – Prague Geoportal