An Introduction to GIS & the Role of Spatial Data

CVEN 2012 – GeomaticsUniversity of Colorado – Boulder

April 2006

Alyssa McCluskey

Sources: Briggs (U of Texas – Dallas), Engel et al. (Purdue University), Martin (CEE), ESRI, ETH

Next 3 WeeksWeek 1• Intro to GIS• Learning ArcGIS Module 1Week 2• Spatial Analyst Module 1• Survey DataWeek 3• Other GIS techniques• Review

Today’s Topics

• What is GIS?• What is a GIS analysis?• What can GIS do?• Data Sources• Data Representation• Example GIS Analyses• GIS Software• ESRI On-Line Courses• Labs

What is GIS?

• Geographic/Geospatial Information Science/System– information about places on the earth’s surface– knowledge about “what is where when”

• Began in mid-1960’s

• a computerized data management system designed to capture, store, retrieve, analyze and report geographic and demographic information (Siemens)

• an organized collection of computer hardware, software, geographic data, and personnel designed to efficiently capture, store, update, manipulate, analyze, and display all forms of geographically referenced information (ESRI-Environmental Systems Research Institute)

GIS Analysis

• A process for looking at geographic patterns in data and at relationships between features

• May be simple (making a map)

• May be complex, using models that combine many data layers

What can GIS do?

• It allows users to quickly:– Search– Display– Analyze– Model (spatially and temporally) information.

• A good GIS should be able to answer the following questions:– Location, conditions, trends, patterns, modeling

What can GIS do?

• Location: What is at…?

10 km

N

What can GIS do?

• Condition: Where is it…?

What can GIS do?

• Trends: What has changed since…?

What can GIS do?

• Modeling: What if…?

Data Sources

Satellites:Satellites:

Configuration of Global Observing SystemConfiguration of Global Observing System

- Geostationary (equator)Geostationary (equator)

- Polar-orbitingPolar-orbiting

Terms

Spatial resolution refers to the area on the ground that an imaging system, such as a satellite sensor, can distinguish. (e.g. datasets 30m, 1m)

Orthophotography: Digital imagery in which distortion from the camera angle and topography have been removed, thus equalizing the distances represented on the image.

LANDSAT

30 m

Spatial Resolution

1 m

Spatial Resolution

Example On-Line Data Sources

• U.S. Bureau of the Censuswww.census.gov– Demographic data, socioeconomic,

agricultural summaries

• U.S. Geological Survey (USGS) www.usgs.gov

• FGDC Clearinghouse (Federal Geographic Data Center)www.fgdc.gov– Access to state and national agency datasets

Data Representation

• Maps: 2-dimensional representation of 2-dimensional world

• Tables: 2-dimensional representation of information

Data Representation

• Multiple maps (or layers) may be analyzed simultaneously

Digital Orthophoto

Streets

Hydrography

Parcels

Buildings

Zoning

Utilities

Administrative Boundaries

Data Representation

• Data is Geo-referenced• Different Map Projections (Mercator, Lambert, Albers

Equal Area, etc.)

Data Representation

• Multiple maps (or layers) may be analyzed simultaneously

Data Representation

roads

hydrology

topography

longitude

longitude

longitude

latitu

de

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

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

latit

ude

latit

ude

Spatial Data - Vector

PointPoint - a pair of x and y coordinates(x1,y1)

LineLine - a sequence of points

PolygonPolygon - a closed set of lines

Node

vertex

Vector data are defined spatially:

Spatial Data – Raster (Grid)

Grided Data

Grids or pixels

Grided Data

Grids or pixels

Grided Data

Grids or pixels

Spatial Data – Raster (Grid)

Spatial Data – Vector & Raster

PointPoint

LineLine

PolygonPolygon

VectorVector RasterRaster

Zone of cells

Raster data are described by a cell grid, one value per cell

Spatial Data – Vector & Raster

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

Raster Representation

line

polygon

point

Vector Representation

Spatial Data – Vector & Raster

Spatial Data – Vector & Raster Mix

Spatial Data – Vector & Raster

Which Type is Better?

• It depends on– The application– The data available – The analysis being conducted

• Take advantage of strengths of each.

• Converting between representations is easy.

Example Analysis: Hydrologic Cycle

Hydrologic Data

GIS Analysis

• Frame the question– What areas of the country receive the most precipitation?– How much of the county is suitable for growing maize?– Where is the best location for a landfill so as to minimize

potential groundwater contamination?

• Understand your data• Choose a method• Process the data• Look at the results

GIS Advantages

• Ability to create and display geo-referenced data

• Ability to query or model and display the results

• Visual and tabular representations (spatial, temporal)

• Represents the real world

• Connections to other modeling tools

GIS Examples

GIS Examples

GIS Software

• ESRI – ArcGIS Desktop –(ArcGIS, ArcInfo, ArcMap, ArcCatalog) (ArcView)

• Open Source Software – GRASS

• Clark Labs - IDRISI

• USING ESRI On-Line Courses

Fill out this form,

ESRI will send you an email for conformation.

Learning ArcGIS Desktop

Complete Module 1

Completing Labs

• Very limited computers • West side of Bechtel Lab and in the TA offices• Your responsibility to complete the labs (don’t wait

until last minute)

• Work together 2-3 people per assignment• Delete the data you downloaded before

logging off• Email me or print certificates and certain maps

from exercises

Some Tips

• Easiest to save data under C:\Temp

• Otherwise click on data and point to location (Rt-Click, Properties, Data Source)

Problems?

• Contact TA if during lab times

• Contact me via email…

• alyssa.mccluskey@colorado.edu

• dralyssamccluskey@yahoo.com

• We’ll address common problems in class lecture or an email to the class.

Lab 1: GIS• Learning ArcGIS Desktop

– Module1

• Create a map showing the potential youth center locations without using the map template. Save this as a jpeg and either email to me or print and hand in. Spend some time making it nice!

• Turn in Module1 Completion Certificate (email or print and turn in)

• Due Monday April 16th

Next Class

• Go over Lab 1: Learning ArcGIS Desktop