GIS: Geography Information GIS: Geography Information SystemsSystems

What is GIS?

a computer-based information system used to: a computer-based information system used to:

What is GISWhat is GIS

capture, capture, manage, manage, update, update, analyze, analyze, display, and display, and output spatial data and informationoutput spatial data and information

to be used in a decision making contextto be used in a decision making context

A GIS (Geographical Information System is:A GIS (Geographical Information System is:

What is GIS?

Components of a GISComponents of a GIS

HardwareHardwareSoftwareSoftware DataData

PeoplePeople ApplicationsApplications

GIS

What is GIS?

Geography Brings Data TogetherGeography Brings Data Together

Multiple Data Layers

Geographically Referenced

Common Coordinate System

Provides basis for:

• Data Integration

• Systematic Analysis

• Customized Maps

What is GIS?

GIS Data Model

A layer-cake of information

What is GIS?

The GIS Data Model: The GIS Data Model: ImplementationImplementation

Geographic Integration of InformationGeographic Integration of Information

Digital Orthophoto

Streets

Hydrography

Parcels

Buildings

Zoning

Utilities

Administrative Boundaries

• Data is organized by layers, coverages or themes (synonomous concepts), with each layer representing a common feature.• Layers are integrated using explicit location on the earth’s surface, thus geographic location is the organizing principal.

What is GIS?

GIS Integrates Data & ApplicationsGIS Integrates Data & Applications

HumanServices

Town Clerk

Senior Center

Parks & Recreation

Town Manager

Finance

Health

Building Police Engineering

Assessor

Planning

Public Works

FireDepartment

What is GIS?

A GIS Manages Two Types of DataA GIS Manages Two Types of Data

Attribute Data (what)information that defines and

describes each feature

Spatial Data (where) cartographic features

points, lines & polygons

What is GIS?

Spatial and Attribute Data Spatial and Attribute Data • Spatial data (where)

– specifies location– stored in a shape file, geodatabase or similar geographic file

• Attribute (descriptive) data (what, how much, when)– specifies characteristics at that location, natural or human-created– stored in a data base table – It is information that is additional to geographical location.

(Spatial Data) E.g. Names, descriptions, labels, statistics, measurements, categories, codes, dates, symbology.

GIS systems traditionally maintain spatial and attribute data separately, then “join” them for display or analysis for example, in ArcView, the Attributes of … table is used to link a shapefile (spatial structure) with a data base table containing attribute information in order to display the attribute data spatially on a map

What is GIS?

The GIS Model: LayeringThe GIS Model: Layering

roads

hydrology

topography

Here we have three layers or themes: --roads, --hydrology (water), --topography (land elevation)They can be related because precise geographic coordinates are recorded for each theme.

longitude

latit

ude

longitude

longitude

latit

ude

latit

ude

Layers are comprised of two data types•Spatial data which describes location (where)•Attribute data specifing what, how much,when

Layers may be represented in two ways:•in vector format as points and lines•in raster(or image) format as pixels

All geographic data has 4 properties: projection, scale, accuracy and resolution

What is GIS?

Layers are represented in Layers are represented in Raster Raster or Vectoror Vector format format

Raster Model• area is covered by grid with (usually) equal-sized, square cells• attributes are recorded by assigning each cell a single value

based on the majority feature (attribute) in the cell, such as land use type.

• Image data is a special case of raster data in which the “attribute” is a reflectance value from the geomagnetic spectrum– cells in image data often called pixels (picture elements)

• Vector ModelThe fundamental concept of vector GIS is that all geographic

features in the real work can be represented either as:• points or dots (nodes): trees, poles, fire plugs, airports, cities• lines (arcs): streams, streets, sewers,• areas (polygons): land parcels, cities, counties, forest, rock

type Because representation depends on shape, ArcView refers to files

containing vector data as shapefiles

What is GIS?

0 1 2 3 4 5 6 7 8 90 R T1 R T2 H R3 R4 R R5 R6 R T T H7 R T T8 R9 R

Real World

Vector RepresentationRaster Representation

Concept of Vector and Raster

line

polygon

point

What is GIS?

Street Network layer: lines Land Parcels layer: polygons

Raster (image) LayerDigital Ortho Photograph Layer:

Digital Ortho photo: combines the visual properties of a photograph with the positional accuracy of a map, in computer readable form.

VectorLayers

Layers

Projection: State Plane, North Central Texas Zone, NAD 83Resolution: 0.5 meters Accuracy: 1.0 metersScale: see scale bar

0 1500 3000 Feet

What is GIS?

Visualizations - Layer ControlVisualizations - Layer Control

What is GIS?

Different Ways to View DataDifferent Ways to View Data

What is GIS?

GIS Applications – What GIS is used forGIS Applications – What GIS is used for

• Property assessment

• Wetlands regulation

• Emergency response

• Infrastructure management

• School redistricting

• Law enforcement

• Open space planning

• Greenway planning

• Access to health services

• Forest management

• Homeland security

• Transportation planning

• Site suitability / selection

• Build-out analysis

• Search and rescue

• Plans of C & D

• Map design & production

• Watershed protection

• Permit review

• E-911

• Farmland protection

• Aquifer protection

• Archaeological research

• Economic development

What is GIS?

Examples of Applied GISExamples of Applied GIS• Urban Planning, Management &

Policy– Zoning, subdivision planning– Land acquisition– Economic development– Code enforcement– Housing renovation programs– Emergency response– Crime analysis– Tax assessment

• Environmental Sciences– Monitoring environmental risk– Modeling stormwater runoff– Management of watersheds,

floodplains, wetlands, forests, aquifers

– Environmental Impact Analysis– Hazardous or toxic facility siting– Groundwater modeling and

contamination tracking

• Political Science– Redistricting– Analysis of election results– Predictive modeling

• Civil Engineering/Utility– Locating underground facilities– Designing alignment for freeways, transit– Coordination of infrastructure

maintenance

• Business– Demographic Analysis– Market Penetration/ Share Analysis– Site Selection

• Education Administration– Attendance Area Maintenance– Enrollment Projections– School Bus Routing

• Real Estate– Neighborhood land prices– Traffic Impact Analysis– Determination of Highest and Best Use

• Health Care– Epidemiology– Needs Analysis– Service Inventory

What is GIS?

Provide examples of data pre-processing.

(1) Georeferencing– The process of giving images in your

GIS real-world coordinates.

(2) Digitising— features on paper-based maps are traced using a mouse type device called a cursor (it is stored in vector format)

(3) Scanning— a scanner converts hardcopy maps and documents into digital images.

(4) Features and Attribute tables— Attributes are attached to the vector feature in the GIS by using a data table. The columns are the different kinds of attributes, the rows are the individual vector features that have been digitized.

What is GIS?

Name and explain 4 steps to follow when creating a GIS project. 1)Data collection. The process of finding data.

2) Data pre-processing. Data is made user-friendly by undergoing distortion adjustments and geometric registration. (See slide on data pre-processing).

3) Data Management. Storing and updating large amounts of data and making it easier for users to find the data.

4) Data Analysis and Manipulation. Data can be analyzed and change into information.

ApplicationsApplications

What is GIS?

What is a GIS project? (Provide some examples of GIS projects).

A Gis project is one that uses spatial / geographical data to answer a particular question:

1) Agriculture: How can food production be improved?

2) Emergency: What is the fastest route to the hospital?

3) Retail: Where is the best to build a new shopping centre?

4) Marketing: Where do the people live that I want to sell to?

What is GIS?

GIS Projects GIS Projects • Locating a Day-care

– intro to GIS capabilities– illustration of a major application: site selection

• Texas Demographic growth– manipulation of data and mapping principles– another major application: analysis of spatial patterns with polygon

data

• Geocoding Housing Sales, or Analyzing Earthquake Locations– techniques and data requirements for geocoding and point

patterns– another application: geocoding/address matching

• Creating a Census Tract layer, or a Geological Map– editing and creating topologically consistent data– how new data layers can be created

• Pipeline Routing– data selection, buffering and spatial analysis– another major application: corridor studies

What is GIS?

Perform Spatial AnalysesPerform Spatial Analyses

Find

Buildings

Within 250m of streams

What is GIS?

Public Utility ApplicationsPublic Utility ApplicationsSelect Suitable Site for Water

Company Well

.

Water Company Service Area

Only within undeveloped land areas

Within undeveloped land area, only outside buffer of polluted streams

and known point sources of pollution.

Only surface geology that shows greatest potential for water production

What is GIS?

How does GIS How does GIS data get stored?data get stored?Data

Decisions

Science

Managem

ent

Many GIS applications store digital data in a database.

GIS data is stored in a number of file formats, but the shape file is the most common. It consists of at least three different files that work together to store digital vector data as shown in the table below.

A database is a storage system linked to tables.

What is GIS?

Sources of data used in a GIS

1)Primary data: Data collected in the field by physically measuring, observing and interpreting objects e.g. GPS measurements, scanned in maps.

2) Secondary data: Data that already exists in one format or another. It is data that can be reused e.g. maps, databases, images and aerial photographs.

Name two ways in which primary data is collected. 1) Ground-based surveys. E.g tachymetry2) GPS

What is GIS?

What is metadata? Metadata is data about data.

Provide some examples of metadata.

Names of people responsible for creating the data.

A textual description of the content of the data.

Dates and times of when the data was produced.

Map projection / spatial resolution used.

What is GIS?

GIS aspects that need agreement on global standardisation include:

•The global map projections used.

•Methods of Georeferencing.

•Geographical names.

•Units of measurement used.

•Methods of processing digital data.

Data Standardisation

Growing of GIS has resulted in intense efforts at data standardisation to establish structures and methods for the interchange of spatial data.

What is GIS?

Data sharing offers several advantages:

•It avoids expensive repetition of data acquisition (e.g. sensors in orbit).

•It makes a wide range of data available to people all over the world.

•It reduces workload and cost

Data Sharing

Data sharing between organisations with different GIScould only be achieved by data converters, transfer standards and open file formats.

What is GIS?

Data is protected in several ways:•Data must be secure from loss or computer failure.•Data must be secure from fraud.•Some files (databases) of municipalities and the government must be kept secret.•The police, fire brigade and ambulance have data files that would be of interest to criminals / terrorists and have to be protected.

Data SecurityData and information can sometimes be highly sensitive, either for commercial or personal confidentiality or national security. To ensure data security the data can only be accessed with authorisation codes.

What is GIS?

Data ManipulationData needed for GIS comes from many different sources. They will need to be transformed or manipulated in some way to make them compatible with the GIS system

Examples of Data Manipulation:Examples of Data Manipulation:

Creation of buffers, creation of models, integration of data layers, conversion of data from raster and vector formats, interpolation between points .

What is GIS?

To correct distortionsTo correct distortions

Why is it necessary to manipulate Why is it necessary to manipulate data in a database?data in a database?

To sharpen definitionsTo sharpen definitions

To ensure colour consistencyTo ensure colour consistency

To ensure correct latitude and To ensure correct latitude and longitudelongitude

Linked database tableLinked database table

Spatial dataSpatial data

What is GIS?

Data Integration

What are the problems of integrating data?

Maps have different scales

Maps have different projections

Maps have different georeferences

What is the importance of integrating data?

A summary of integrated data is produced and is easier to understand

Data integration involves the combination of two or more layers in order to create a new one.

What is GIS?

Data Querying

You can begin to ask questions:

GIS allows querying in order to answer Geographical questions and help solve complex problems. It’s displayed graphically!

The vegetation layer is compared with the soil data layer. The shrubs and sand areas are overlaid and only the areas adhering to the query are shown.

What is GIS?

Answers to Simple QuestionsAnswers to Simple Questions

?

Visualize spatial relationships

Answer questions about what “it” is

Answer questions about where things are

Ad hoc queries are one of the most important and basic of all GIS functions

Ad hoc queries are one of the most important and basic of all GIS functions

What is GIS?

• That were sold in the past 3 years

• For more than $200,000

Queries - Class of FeaturesQueries - Class of Features

• Select all parcels in a subdivision

What is GIS?

A buffer refers to an area around a point, line or polygon.You can demarcate a buffer area of for example 3 km around a place on the map.

EXAMPLES OF BUFFERING: What is the total number of customers within 10 km of this shopping mall? Which areas will be affected by a 1m rise in sea level? Which residential areas will be affected by a nuclear fallout affecting a radius of 60 km from the nuclear power station?

MapInfoMapInfo

Buffering

What is GIS?

Statistical Analysis

Information such as:

Statistical Analysis is used to investigate GIS data and assist in the identification of additional information.

Spatial patternsSpatial trendsClimatic averages e.g. temperature and rainfall

Which layers would GIS researches use to determine the risk of a landslide:

Altitude Slope angleRock type Land coverSlope exposure Distance from riversProfile curvature Surface curvature Distance from the road Drainage Basin

What is GIS?

What remote sensing is used for: Remote sensing is obtaining data from a distance without touching the object.

Instruments used to collect the information are the camera, radar, sonar, thermal and electro-optical sensors.

Remote sensing is used to study weather patterns, climate change, urban change, the atmosphere, landscapes, ecosystems, human impact on the environment, the oceans and hydrology.

What is GIS?

Spatial ResolutionSpatial Resolution

• Satellite images are captured in digital format.• They consist of a very fine grid of squares called

‘picture cells’ or ‘pixels’. (Raster data)• Coarse (low) resolution if the pixel covers a

large area on the ground• Fine (high) resolution covers a smaller area

on the ground.

Spatial Resolution refers to the size of an object that can be recorded; the most usual method is the pixel size.

What is GIS?

Spectral ResolutionSpectral ResolutionSpectral resolution refers to the width of the wavelength intervals that are being measured in the electromagnetic spectrum.

Remote sensors can collect data in the visible part of the spectrum (to provide images such as aerial photographs).

Other sensors may collect data in the invisible sectors like infrared (seen below) and ultraviolet.

What is GIS?

Vertical Aerial Photograph – Taken from above, camera is pointing vertically downwards.

High Oblique Aerial Photograph – Horizon is visible. Camera is tilted at 68 degrees.

Low Oblique Aerial Photograph – Horizon is not visible. Camera is tilted at 30 degrees.