GIS is a system for managing and analyzing geographic data. It uses two main data models: vector, representing points, lines and polygons; and raster, representing data as a grid of cells. Common file formats include shapefiles for vector data and GeoTIFF and MrSID for raster. GIS data is referenced using coordinate systems like WGS84 for global latitude/longitude or HK80Grid for Hong Kong. ESRI's ArcGIS software allows viewing, editing, and publishing this geospatial data for mapping and analysis.

1. Introduction to
GIS
Joey Li
joeylicc@gmail.com
@joeylicc
joeylicc.wordpress.com

2. 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.

3. 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 GIS
1. Vector data model
2. Raster data model

4. Data Representation (Vector)
A coordinate-based data model that represents geographic
features as points, lines, and polygons.
1. Points
Location of Wells, Schools, or Points
of Interest
2. Lines / Polylines
Road Centerlines, Rivers, Trails, or
Streets
3. Polygons
Boundary of Cities, Lakes, or Forests

5. Data Representation (Raster)
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.
Raster as Satellite Imagery
Raster as Elevation Surface

6. 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)

7. 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

8. ESRI ArcGIS for Server
● Publishing GIS
Web Services
● Creating Web
Mapping
Applications
● Administering
ArcGIS for Server

9. Geodatabase (ArcSDE)
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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.

10. 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

11. 3 Takeaways
1. GIS data represents real world objects in layers
2. There are 2 major data model in GIS
a. Vector = Point, Line, Polygon
b. Raster = Cells with Values
3. Global Coordinate System = WGS84 (Sphere)
HK Coordinate System = HK80Grid (Flat)

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