Geographic Information Systems Module...Google Maps / Earth Microsoft Live Local Intergraph – Geomedia Environmental Systems Research Institute - ArcGIS Introduction to GIS – GE158

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Introduction to GIS – GE158 – January, 2007

Introduction toGeographic Information Systems

[email protected]

The Environmental And Remote TecHnologies LabMacMillan Hall, Room 105

http://www.brown.edu/Research/Earthlab/


Outline• Environmental and Remote TecHnologies Lab

• What is GIS

• GIS software – the ESRI Suite

• Software demonstration

• The basics of spatial data files– Categories– File formats

• Finding spatial data files

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Environmental And Remote TecHnologies Labaka EARTH Lab

•Room 105 MacMillan Hall

•Dedicated to GIS and Remote Sensing

•Ten workstations / Server

•Large format plotter

•Large format digitizing board

•2 Small format printers

•GPS

•Open schedule

•http://www.brown.edu/Research/Earthlab


What Is A Geographic Information System

A GIS is unique because it is:

• Interdisciplinary•Natural Sciences•Engineering•Social Sciences•Health

•Depiction and Modeling

•Solving Real World Problems

•Dynamic

A combination of computer hardware and software that allows for the utilization, creation and analysis of digital data files that are location based – ie. Spatial.

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Vendors of GIS Software Products

Caliper Corporation – Maptitude

Manifold – Manifold System 5.00

Clark Labs – Idrisi

Autodesk – Autodesk Map 2004

Google Maps / Earth

Microsoft Live Local

Intergraph – Geomedia

Environmental Systems Research Institute - ArcGIS


GIS Software Suite by ESRI

ArcIMS

ArcGIS Server

ArcExplorer

ArcPad

MapObjects

ArcReader

ArcView

ArcGIS Desktop

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Two Interdependent Graphical Interfaces•ArcCatalog – the file manager•ArcMap – the “viewing” environment

Three “Tiers”• ArcView 9.2• ArcEditor 9.2• Arc/Info 9.2

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ArcToolBox – a suite of tools designed to process spatial data (located ‘inside’ ArcCatalog and ArcMap)

ArcGIS Desktop 9.2 Software


Demonstration

Using GIS to Delineate Watersheds

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Spatial Data File Basics1) Not your average .doc document

a) Complex architectureb) location is embeddedc) Attribute data in a relational database is linked

2) Digital Representations of Features / Eventsa) surface, subsurface, atmosphereb) natural or “man-made”b) earth or other planetary bodies

3) Collectively Referenced by many generic namesa) Geospatial Data, Geographic Data, GIS Data,

Layers, Themes

4) Spatial Data Files fall into 1 of 2 possible typesa) Vectorb) Raster


Vector Spatial Data

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Monitoring Stations

Stream Outlets

Bridges

Dams

Stormwater Discharges

Vector Spatial DataGeographic Features as Points

Example Layers


Streams

Roads

Canals

Pipes / Conduits

Vector Spatial DataGeographic Features as Lines

Example Layers

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Watersheds

Lakes

Wetlands

Soils

Land Use

Vector Spatial DataGeographic Features as Polygons / aka Polylines

Example Layers


Vector Spatial Data

Attributes

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Vector Spatial Data

Geographic Representation & Attributes are linkedEvery Record has a corresponding Feature


Advantages

Spatial context

Measurements

Coincidence

Queries

Vector Spatial Data

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•Features are represented by a continuous surface

•Each pixel has a numeric value•Text values possible – infrequent

• Pixel values may be• actual measurements• color values (0 – 255)• thematic representations

• Each pixel encompasses a square unit of surface area

• Some pixels can be coded as “No Data”

Raster Spatial Data


Raster Spatial Data

Pixel Values represent actualmeasurements of Elevation

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Raster Spatial Data

Pixel Values are used to assign gray scale or true color values


Raster Spatial Data

Pixel Values are used to represent categories

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Raster Spatial Data

Advantage = Performance of Mathematical Operations


Spatial Data File Formats

1. Coverage• Vector based• Supports representation of geographic features as points, lines, or

polygons• Relational database (holding attributes) is “Info”

• software that predates windows operating system• Complex structure on the disk (two folders and a multitude of files)• Topology

2. Shapefile• Vector based• Supports representation of geographic features as points, lines, or

polygons• Relational database (holding attributes) is “dBase”• Structure is less complex on the disk, but still confusing at first• No topology (unless converted from a coverage)

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Spatial Data File Formats3. Grid

• Raster based• Values can be integers, floating point• Complex structure on the disk (two folders and a multitude of files)

4. Image files• Raster based• .jpg .tif .sid .bmp .png• Structure is less complex on the disk• Orthophotographs / Georeferencing

5. Geodatabase• Superseding coverages, shapefiles, grids, images• A “container” – one file on disk holds everything• Coverages and shapefiles become “feature classes”• Grids and Images become “rasters”• Two types: personal and multi-user

• Personal = Microsoft Access• Multi-user = Oracle, SQL Server, IBM DB2; Informix


Coordinate Systems

Where am I?

Where are you?

Where is the lake/stream/

monitoring station?

How do I get there?

What is the distance?

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Coordinate Systems

Two Categories

1) Geographic 2) Projected


Geographic Coordinate Systems

Properties

•Earth maintained as a sphere

•Datum (sphere measured differently)

•Latitude and Longitude define locations

•Latitude = North or South of Equator = Y

•Longitude = East or West of Prime Meridian = X

•Units = degrees, minutes, seconds (decimal degrees)

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Available in ArcGIS

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The Downfall of Geographic Coordinate Systems

While longitude and latitude can locate exact positions on the surface of the globe, they are not uniform units of measure

You can’t measure distances or areas

accurately or display the data easily on a flat map

or computer screen

Square Degrees?

1 degree of longitude ranges from 0 to 111 km


Projected Coordinate Systems

Properties

•Earth NOT maintained as a sphere – a Projection is applied to “flatten” it

•Datum (sphere measured differently)

•X is a position along the horizontal plane from an origin

•Y is a position along the vertical plane from an origin

•X & Y become a “coordinate pair”

•Units = meters or feet

Projection = mathematical equations which translate locations on a

spherical surface to a two-dimensional plane

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Conic Projections

Planar Projections

Cylindrical Projections


The mathematical equations (the “projection”) which translate locations on a spherical surface to a two-dimensional plane fall into one of three categories:



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Available in ArcGIS


The Downfall of Projected Coordinate Systems

Distortion of Geographic Features

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Spatial Data Files and Coordinate Systems in ArcGIS Desktop

2) ArcMap does not “like it” when the coordinate system of a spatial data file has not been explicity “Defined”

• the *.prj file

1) In a research project, you probably will obtain spatial data files that are “undefined” or have different coordinate systems

• Conversion•Errors with certain tools/procedures•Warning messages•Data files that don’t line up


Where to find spatial data files

Federal AgenciesNOAA FDAEPA FEMAUSGS CDC

State GIS Programs

MassGIS http://www.mass.gov/mgis/massgis.htm

RIGIS http://www.edc.uri.edu/rigis/

Municipalities or Counties (not so much in RI)

Academic InstitutionsEARTH Lab Server

Private Data Developers (expensive)

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Demonstration

Georeferencing

Documents

Geographic Information Systems Module...Google Maps / Earth Microsoft Live Local Intergraph – Geomedia Environmental Systems Research Institute - ArcGIS Introduction to GIS – GE158