An Introduction to GIS & the Role of Spatial Data CVEN 2012 – Geomatics University of Colorado –...
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Transcript of An Introduction to GIS & the Role of Spatial Data CVEN 2012 – Geomatics University of Colorado –...
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…
• 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