1. Dr. David Liu

2. Objectives Understand what a GIS is Understand how a GIS functions
Spatial data representation
GIS application

3. What is an Information System?
In the digital environment we use software to create complex information systems.
Database
Some software is optimized for manipulating databases. MS Access is an example of this. Modern database management programs utilize a relational database. This is a database that references each piece of information once and then keeps track of the relationships among them. In this way
Management

4. What is a GIS? + Information System A means of storing,
retrieving, sorting,
and comparing
spatial data
to support some
analytic process. +
Geographic Position
A GIS can be best defined by defining the two parts of the term; geography and information system.
Geography is a science that deals with the earth and life on the earth, while an information system is a way to capture, store, retrieve, sort, and process data to support some analytic process.

5. What is a GIS? GEOGRAPHIC Information System
What makes the Information System geographic?
The user needs to begin spatially!
GIS links graphical features (entities) to tabular data (attributes)

6. GIS Definition
A GIS is a system (hardware + database engine) that is designed to efficiently, assemble, store, update, analyze, manipulate, and display geographically referenced information (data identified by their locations).
A GIS also includes the people operating the system and the data that go into the system.
A geographic information system (GIS) is a computer-based tool for mapping
and analyzing things that exist and events that happen on Earth. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps. These abilities distinguish GIS from other information systems and make it valuable to a wide range of public, military and private enterprises for explaining events, predicting outcomes, and planning strategies. Whether siting a military base camp, finding the best soil for a tank to maneuver on, or figuring out the best low level air route for a bombing raid. Map making and geographic analysis are not new, but a GIS performs these tasks better and faster than do the old manual methods. And, before GIS technology, only a few people had the skills necessary to use geographic information to help with decision making and problem solving. Today, GIS is a multi-billion-dollar industry employing hundreds of thousands of people worldwide. GIS is taught in schools, colleges, and universities throughout the world. Professionals in every field are increasingly aware of the advantages of thinking and working geographically.

7. Database Management System
Key Components of GIS
Spatial Data Modeling
Visualization
Spatial Analysis
&
Spatial modeling
Spatial Data
&
Attribute Data
A geographic information system (GIS) is a computer-based tool for mapping
and analyzing things that exist and events that happen on Earth. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps. These abilities distinguish GIS from other information systems and make it valuable to a wide range of public, military and private enterprises for explaining events, predicting outcomes, and planning strategies. Whether siting a military base camp, finding the best soil for a tank to maneuver on, or figuring out the best low level air route for a bombing raid. Map making and geographic analysis are not new, but a GIS performs these tasks better and faster than do the old manual methods. And, before GIS technology, only a few people had the skills necessary to use geographic information to help with decision making and problem solving. Today, GIS is a multi-billion-dollar industry employing hundreds of thousands of people worldwide. GIS is taught in schools, colleges, and universities throughout the world. Professionals in every field are increasingly aware of the advantages of thinking and working geographically.
Database Management System

8. RASTER VECTOR Real World Spatial Data Modeling
Spatial data is essentially data with a location. It contains information about the location and shape of, and relationship among geographic features usually stored as coordinates. Spatial data comes in two types, VECTOR and RASTER. Geographic information systems work with two fundamentally different types of geographic models--the "vector model" and the "raster model."

9. Raster Representing Spatial Elements
Stores images as rows and columns of numbers with a Digital Value/Number (DN) for each cell.
Units are usually represented as square grid cells that are uniform in size.
Data is classified as “continuous” (such as in an image), or “thematic” (where each cell denotes a feature type.
Numerous data formats (TIFF, GIF, ERDAS.img etc)
A raster image comprises a collection of grid cells rather like a scanned map or picture. Both the vector and raster models for storing geographic data have unique advantages and disadvantages.
Raster models do not provide precise locational information because space is divided into discrete grid cells. The assumption is that a point can be found within a grid cell.

10. Representing Spatial Elements
Vector
Allows user to specify specific spatial locations and assumes that geographic space is continuous, not broken up into discrete grid squares
We store features as sets of X,Y coordinate pairs.
In the vector model, information about points, lines, and polygons is encoded and stored as a collection of x,y coordinates. A single x, y coordinate, can describe the location of a point feature, such as a control tower. Linear features, such as roads and rivers, can be stored as a collection of point coordinates. Two coordinate pairs are enough to show location and orientation in space. Polygonal features, such as an area of operations and lakes, can be stored as a closed loop of coordinates. The vector model is extremely useful for describing discrete features, but less useful for describing continuously varying features such as soil type.
Spatial data is unique to a GIS in that there are two aspects two it. It has a location and an attribute. The location can be either a geographic coordinate, MGRS coordinate, or any other (x,y) coordinate. The attribute can be either adjectival (describing the object) or have a magnitude (a numerical value).

11. Entity Representations
We typically represent objects in space as three distinct spatial elements:
Points - simplest element
Lines (arcs) - set of connected points
Polygons - set of connected lines
We need symbolize spatial features in order to be able to associate attribute information.
We can classify different features into different dimensions. Each classification of dimension is a conceptual classification.
Points - “0” dimensionality. No length or Width.
Each point is Discrete in that it can only occupy a given point in space at any given time.
Lines - “1” dimensional. Length, but No Width.
Must have a beginning and an ending point.
Polygons - “2” dimensional. Length and Width.
By adding Width, we can describe a feature as having an area.
Surfaces - “3” dimensional. Length, Width, and Height.
Surfaces have infinite number of values (e.g. Elevation). We say that this type of data is Continuous.
When thinking of spatial elements, we must consider Spatial Scale. Depending on scale, we may want to represent a river as a line or a polygon.
We use these three spatial elements to represent real world features and attach locational information to them.

12. Attributes
In the raster data model, the cell value (Digital Number) is the attribute. Examples: brightness, landcover code, SST, etc.
For vector data, attribute records are linked to point, line & polygon features. Can store multiple attributes per feature. Vector features are linked to attributes by a unique feature number.

13. Linking Spatial Entity with Attributes
1 (Universe polygon)
Spatial data 2 3 3
(ARC functions) 4 5
Storage: For small GIS projects it may be sufficient to store geographic information as simple files. There comes a point, however, when data volumes become large and the number of data users becomes more than a few, that it is best to use a database There are many different designs of DBMSs, but in GIS the relational design has been the most useful. A DBMS is nothing more than computer software for managing a database--an integrated collection of data. In the relational design, data are stored conceptually as a collection of tables. Common fields in different tables are used to link them together. This surprisingly simple design has been so widely used primarily because of its flexibility and very wide deployment in applications both within and without GIS.
COV# ZONE ZIP 1 2
C-19
22060
Attribute data 3
A-4
22061 3
A-4
22061 4
C-22
22060
(INFO or TABLES functions) 5
A-5
22057

15. Raster Advantages Vector Advantages
Raster vs. Vector
Raster Advantages
The most common data format
Easy to perform mathematical and overlay operations
Satellite information is easily incorporated
Better represents “continuous”- type data
Vector Advantages
In Raster we explicitly store attribute information and imply its location based on the position within the grid cell structure.
In Vector, we explicitly store the entity information and where the entity is located. We rely on a database structure to link to attribute information.
Accurate positional information that is best for storing discrete thematic features (e.g., roads, shorelines, sea-bed features.
Compact data storage requirements
Can associate unlimited numbers of attributes with specific features

16. Visualization

17. Visualization

18. Spatial Analysis/Modeling
Spatial Operation
Buffering
Overlay
Spatial Statistics
Analysis and M a n i p u l a t i o n: It is likely that data types required for a particular GIS project will need to be transformed or manipulated in some way to make them compatible with your system. For example, geographic information is available at different scales (street centerline files might be available at a scale of 1:100,000; Topographic line maps data such as ITD at 1:50,000). Before this information can be integrated, it must be transformed to the same scale. This could be a temporary transformation for display purposes or a permanent one required for analysis. GIS technology offers many tools for manipulating spatial data and for weeding out unnecessary data.
Spatial Data Mining

19. Buffer: Delineation of a zone around
Proximity Analysis
Buffer: Delineation of a zone around
the feature of interest within a given distance.
For a point feature, it is simply a circle with
its radius equal to the buffer distance.

20. Buffer Example Rural district in N.E. Thailand 51 study villages:
evaluate land use in the district relative to population change
Need to determine types & quantities of land use surrounding each village:
generate 3-km buffers around village centroids
overlay buffers on land-cover classification generated from satellite imagery
use buffers to “cut out” land near each village and summarize land uses within “cut out” area

21. Variable Distance Buffer
Buffer zone can be made variable
according to certain attributes.
Suppose we have a point pollution
source, such as a power plant. We
certainly want to keep our residential
area away a distance from it.
However, this distance can be made
variable according to the amount of
pollution that a power plant produces.
For small power plant, the distance can
be short, while for large power plant that
generate a lot of pollutant, we should
keep a longer distance from it. As we
is shown on the right.

22. Buffers for lines and Polygons
Move circle of specified radius along lie
(or lines forming polygon)
Draw orthogonal from line to edge of circle
Buffer line is tangent to circle where the
orthogonal intersects it.

23. Lines and Polygons Buffer Example
Buffer lines
Buffer polygons

24. Spatial Analysis
Overlay function creates new “layers” to solve spatial problems
The overlay operation is one the most powerful functions in a GIS. It gives the user the ability to place the cartographic representation of thematic data over one another.
However, this is hardly a new function developed by a GIS, but it has been revolutionized by the use of the computerized GIS.

25. Spatial Operation with Multiple Vector Layers
Overlay analyses
Operate on spatial entities from two or more maps to determine spatial overlap, combination, containment, intersection…etc.
one of the most “fundamental” of GIS operations
formalized in 1960s by landscape architects who used acetate map overlays
now a basic part of the GIS toolbox
Vector overlays-
combine point, line, and polygon features
computationally complex
Raster overlays-
cell-by-cell comparison, combination, or operation
computationally less demanding

26. Spatial Operation with Multiple Vector Layers
Basic idea:
spatially combine/compare two data layers to:
(a) generate new output data layer, or
(b) assign attributes of one data layer to another
most cases: one of the data layers will contain polygon entities
Point-in-polygon overlay 
increasing conceptual and computational complexity

27. Point-in-polygon vector overlay
Overlay point layer (A) with polygon layer (B)
in which B polygon are A points spatially located?
» assign polygon attributes from B to points in A A B
Example: comparing soil
mineral content at sample
borehole locations (points)
with landuse (polys)...

28. Line-in-polygon vector overlay
Overlay line layer (A) with polygon layer (B)
in which B polygons are A lines spatially located?
» assign polygon attributes from B to lines in A
Example: assign landuse attributes (polys) to streams (lines)... A B

29. Polygon-polygon vector overlay
Overlay polygon layer (A) with polygon layer (B)
result: what are the spatial polygon combinations of A and B?
» generate new data layer with combined polygons
attributes from both polygon layers are included in output
How are polygons combined?
(i.e. what geometric rules are used for combination?)
UNION (Boolean OR)
INTERSECTION (Boolean AND)
IDENTITY
Polygon overlay will generally result in a significant increase in the number of spatial entities in the output
can result in output that is too complex too interpret

30. Boolean Operations A B A B UNION A A B B INTERSECT
Some of the fundamental overlay analysis for vector data are UNION,
and INTERSECT corresponding to Boolean operations of OR, AND A B A B
UNION OR A A B B
INTERSECT
AND

31. Polygon-polygon vector overlay (cont’d.)
UNION
overlay polygons and keep areas from both layers
INTERSECTION
overlay polygons and keep only areas in the input layer that fall within the intersection layer
IDENTITY
overlay polygons and keep areas from input layer

32. GIS Application – site selection
Talk to each one relevant to the audience.

36. GIS software ESRI products: ArcGIS, Arc/Info … MapInfo
AutoDesk products: AutoCAD
Clark University: IDRISI
GRASS

37. Database Management System
Summary
Spatial Data Modeling
Visualization
Spatial Analysis
&
Spatial modeling
Spatial Data
&
Attribute Data
A geographic information system (GIS) is a computer-based tool for mapping
and analyzing things that exist and events that happen on Earth. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps. These abilities distinguish GIS from other information systems and make it valuable to a wide range of public, military and private enterprises for explaining events, predicting outcomes, and planning strategies. Whether siting a military base camp, finding the best soil for a tank to maneuver on, or figuring out the best low level air route for a bombing raid. Map making and geographic analysis are not new, but a GIS performs these tasks better and faster than do the old manual methods. And, before GIS technology, only a few people had the skills necessary to use geographic information to help with decision making and problem solving. Today, GIS is a multi-billion-dollar industry employing hundreds of thousands of people worldwide. GIS is taught in schools, colleges, and universities throughout the world. Professionals in every field are increasingly aware of the advantages of thinking and working geographically.
Database Management System