Introduction to GIS

Introduction to GIS

Joey Lijoeylicc@gmail.com

@joeyliccjoeylicc.wordpress.com

What is GIS?

GIS = Geographic Information System

A GIS integrates hardware, software and data for capturing, managing, analyzing, and displaying all forms of geographically referenced information.

Data Representation

● GIS data represents real world objects (e.g. roads, land use, elevation, trees, waterways, etc.)

● There are 2 broad methods used to store data in GIS1. Vector data model2. Raster data model

Data Representation (Vector)

1. PointsLocation of Wells, Schools, or Points of Interest

2. Lines / PolylinesRoad Centerlines, Rivers, Trails, or Streets

3. PolygonsBoundary of Cities, Lakes, or Forests

A coordinate-based data model that represents geographic features as points, lines, and polygons.

Raster as Elevation Surface

Data Representation (Raster)

Raster as Satellite Imagery

A spatial data model that defines space as an array of equally sized cells arranged in rows and columns. Each cell contains an attribute value and location coordinates.

Common GIS Data Format

Vector Data Model● Shapefile (.shp, .shx & .dbf)● Geography Markup Language GML (.gml)● Personal Geodatabase (.mdb)● File Geodatabase (.gdb)

Raster Data Model● Enhanced Compressed Wavelet ECW (.ecw)● GeoTIFF = TIFF file with GeoReference (.tif)● MultiResolution Seamless Image Database MrSID (.sid)● JPEG2000 = JPEG file with GeoReference (.jpg)

Coordinate Systems

Geographic Coordinate Systems● WGS84 (Latitude and Longitude) is the most

commonly used Geographic Coordinate System● Hong Kong = 22° 16′ 42″ N, 114° 9′ 32″ E

Projected Coordinate Systems● Project the earth 3D curved surface to a 2D flat surface● Hong Kong 1980 Grid (HK80Grid) is the coordinate

system for Hong Kong GIS data

ESRI ArcGIS for Server

● Publishing GIS Web Services

● Creating Web Mapping Applications

● Administering ArcGIS for Server

Geodatabase (ArcSDE)

● ArcSDE = Spatial Database Engine● Core component of ArcGIS for Server● Primary data storage model for ArcGIS● Centralized location to access and manage spatial data● Major Features

○ Versioning○ Geodatabase Replication○ Geodatabase Archiving

● Support Microsoft SQL Server, Oracle, etc.

ESRI ArcGIS for Desktop

ArcMap● View, Edit and Query geospatial data, and Create

Maps

ArcCatalog● Manage geospatial data● Browse datasets, files, database or other sources

3 Takeaways

1. GIS data represents real world objects in layers

2. There are 2 major data model in GISa. Vector = Point, Line, Polygonb. Raster = Cells with Values

3. Global Coordinate System = WGS84 (Sphere)HK Coordinate System = HK80Grid (Flat)

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