GIS 1 Geographic Coordinates. GIS 2 Geographic Coordinate System Spherical coordinates based on angles of rotation of a radius anchored at earth’s center

GIS 1

Geographic Coordinates

GIS 2

Geographic Coordinate System

•Spherical coordinates based on angles of rotation of a radius anchored at earth’s center

•Latitude and longitude

•Used by many world and federal agencies (e.g. U.S. Census Bureau)

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Lat/Long coordinates Degrees, minutes, and seconds (DMS):

•40° 26′ 2″ N latitude

•80° 0′ 58″ W longitude

Decimal degrees (DD)• 1 degree = 60 minutes,

• 1 minute = 60 seconds

• 40° 26′ 2″ =

• 40 + 26/60 + 2/3600 =

• 40 + .43333 + .00055 =

• 40.434°

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Lat/long coordinates

Translated to distance•1° = 24,859.82 / 360 = 69.1 miles

•1′ = 24,859.82 / (360 * 60) = 1.15 miles

•1″ = 24,859.82 * 5,280 / (360 * 3,600) = 101 feet

World circumference through the poles is 24,859.82 miles

Length of the equator is 24,901.55 miles

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Longitude lines° Longitude (prime meridian)0

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Prime Meridian (Greenwich England)

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Latitude lines

° Latitude (equator)0

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Latitude and longitude

Pittsburgh, PA USA

-80

40

Coordinates

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Map Projections

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Map projections

•Way to represent the curved surface of the Earth on the flat surface of a map

•Each map projection has advantages and disadvantages

•depends on the scale of the map•purposes for which it will be used•some projections are good for

-small areas-areas with a large east-west extent-areas with a large north-south extent

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Map projections

http://www.nationalatlas.gov/articles/mapping/a_projections.html#two

CylindricalPlanar Conic

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Conformal projection

•Cylindrical projection

•Parallels and meridians at right angles

•Preserves angles and shapes of small objects

•Distorts the size/shape/area of large objects

•Seldom used for world maps

Example: Mercator projection (1569)

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Equivalent Projection•Conic projection

•Preserves accurate area

•Scale and shape are not preserved

•Standard projection for U.S. Geological Survey, U.S. Census Bureau

Example: Albers Equal Area

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Compromise Projections•Good for viewing entire world

•Neither equivalent nor conformal

•Meridians curve gently

•Doesn’t preserve properties, but “looks right”

•Used by Rand McNally and the National Geographic Society

Example:Robinson projection (1961)

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•Small-scale maps-Comparing shapes, areas, distances, or directions of map features -Natural appearance desired

New YorkNew York

Los Angeles

When projection is important

Los Angeles

Projection: MercatorDistance: 3,124.67 miles

Projection: Albers equal areaDistance: 2,455.03 miles

Actual distance: 2,451 miles

Los Angeles

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When projection is not important

•Many business, policy, and management applications-Concerned with the relative location of different features

•On large scale maps-Error is negligible

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Rectangular Coordinate Systems

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Rectangular coordinate systems

UTM (U.S. military)State Plane (local U.S. governments)

•Cartesian coordinates (x,y)

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Universal Transverse Mercator (UTM)

•Developed by U.S. Army Corps of Engineers (1940s)

•Covers world, 80°S to 80°N

•Metric coordinates

•Not a single projection but 60 tuned Transverse Mercator projections

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State Plane Coordinate System

•Established by the U.S. Coast and Geodetic Survey in 1930s

•Used by local U.S. governments

•Rectangular coordinates (all positive coordinates in feet or meters)

•Originally North American Datum (NAD 1927)

•More recently NAD 1983 and 1983 HARN

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State Plane zones

•125 zones -At least one for each state-Cannot have zones joined to make larger regions-Follow state and county boundaries

•Each zone has its own, tuned projection-Lambert conformal projection for zones with east-west orientation-Transverse Mercator projection for zones with north-south orientation

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State Plane zones

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Pittsburgh Neighborhoods as State Plane Coordinates

•1983, Pennsylvania South, Feet

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ArcGIS projection tip• GIS map layers in different projections have different coordinate systems

and thus will not overlay each other unless they have spatial reference data in a .prj file

• Assign projections according to the agency

U.S. Census Files • Federal agency• Block groups• Geographic coordinate system

City of Pittsburgh• Local planning agency• Sidewalks• State plane coordinate system

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ArcGIS projection tip• The first layer added in ArcMap sets the “map projection”• Additional layers will overlay properly as long as the correct .prj file is

included• Example: Sidewalks added first (state plane), block groups match even

though they are geographic coordinate system (gcs) projection

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GIS Data Sets

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GIS Data Sets

• ArcInfo Coverages• ArcView Shapefiles• Annotation Layers• CAD Files• Aerial Photos

Copyright – Kristen S. Kurland, Carnegie Mellon University

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ArcGIS

•Integrated collection of GIS software products•ArcGIS framework deploys GIS functionality and business logic wherever it is needed—in desktops, servers (including the Web), or mobile devices. -Desktop GIS (ArcView, ArcInfo, ArcReader, ArcEditor, ArcGIS Extensions, ArcExplorer)-Server GIS (ArcIMS, ArcGIS Server)-Mobile GIS (ArcPAD)


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ArcInfo

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ArcInfo Coverages

AAT Arc Attribute TableARC Arc coordinates and topologyBND Coverage minimum and maximum coordinatesCNT Polygon centroid tablePAL Polygon topologyPAT Polygon/Point Attribute TableTIC Tic coordinates and IdsDBF Database Table

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ArcInfo Coverages•Advantages-Many feature types

•Disadvantages-Cannot edit in ArcMap


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Coverage Attribute Table•Polygon Coverage


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Coverage Attribute Table•Point Coverage


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Coverage Attribute Table•Line Coverages


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ArcInfo Export files•.e00 export exchange file•ArcToolbox translates into ArcGIS•Creates Coverages


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ArcView Shape Files

Advantages•heads-up digitizing and editing•less storage/rapid display •can convert from ArcInfo coverage and back•can export to CAD

Disadvantages•one feature type•no area or perimeter


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ArcView Shape Files

From 3 to 5 Files•.shp - stores feature geometry•.shx - stores index of features•.dbf - stores attribute data•.sbn and .sbx - store additional indices


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ArcView Shapefiles


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Annotation Layers


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Annotation Layers• Separate independent layers• Can be turned on/off


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CAD Files Why CAD Drawings?

• Better Precision for Digitizing -AutoCAD-Microstation


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Aerial Photos

Combining Grid and Vector Maps


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XY Event Tables

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XY Data (Event Files) Data table that includes map coordinates, such as latitude and longitude or projected coordinates

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Event Files

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Exporting Event Files

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GIS Data Sources

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Common Sources

•U.S. Census Bureau

•Geospatial One Stop

•U.S. Geological Survey

•Esri

•Historic websites

•Colleges and universities

•International sites

•State agencies

•Local agencies or engineering firms

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U.S. Census TIGER/Line® Files

http://www.census.gov/geo/www/tiger/

Topologically Integrated Geographic Encoding and Referencing files -Census Bureau’s product for digital mapping of the U.S.-TIGER maps are available for the entire U.S. and its possessions

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Census TIGER/Line® Files

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State Census Tracts (2000)

County sub-divisionsBetween 1,000 and 8,000 people or 1,700 housing units and 4,000 peopleHomogeneous population characteristics (e.g. economic and living)Normally follow visible featuresMay follow government boundaries or other non-visible features

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County Census Tracts (2000)

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City Census Tracts (2000)

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Census Block Groups (2000)

Census tract sub-divisions400 housing units, with a minimum of 250 and maximum of 550Follow visible features such as roads, rivers, and railroads

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Census Blocks (2000)

Smallest geographic area for which the U.S. Census Bureau collects and tabulates decennial census informationBlock boundaries are visible (street, road, stream, shoreline, etc) or non-visible (county or city limits, property lines, etc.)

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U.S. Census data tablesAmerican FactFinder

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http://factfinder.census.gov/

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2000 Summary File Tables

Summary File 1 (SF1) Short form, entire population•Population•Age•Sex•Race•Families•Households•Housing units

Tracts, block groups, blocks

Summary File 3 (SF3) Long form, 1 in 6 households, randomly• Income, poverty•Educational attainment•Citizenship•Employment, workplace,

disability•Transportation, travel time to

work•Detailed housing attributes,

housing value, residency 5 years previous

•Languages spoken, ancestry

Tracts, block groups

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http://factfinder2.census.gov/main.html

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2010 Data Release Schedule http://www.census.gov/population/www/cen2010/glance/

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Data Ferret

http://dataferrett.census.gov/

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Spatial data infrastructure

•Federal Geographic Data Committee-Established by presidential order-Responsible for standards, policies, web portals-Geospatial One Stop, http://gos2.geodata.gov

Base maps and spatial data produced by governments for the public good

Non-rivalrous and non-excludable consumption

Widely-used structures needed for society and enterprises to function

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Physical features:U.S. Geological Survey

•National Map Orthoimagery, replacing the Digital Orthophoto Quadrangles-High-resolution, seamless images in UTM coordinates-Rectified to remove distortions-1m resolution with 0.5 m or 1 ft in urban areas, natural color

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•National Elevation Data set (NED)-Replaces the Digital Elevation Model (DEM)-Seamless raster map with 30m resolution for nation and 10m or better in some areas

Hillshade NED map for Rockville, MD

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•Land cover-Natural and manmade surface features-Collected from satellites in 1992, 2001

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Physical features: U.S. Geological Survey

•National Map Hydography Dataset (NHD)-Water bodies, lines, and points-Identifies segments (reaches) with network coding (flow and direction)

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ESRI’s Website http://www.esri.com/data/resources/geographic-data.html

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National Historic GIS

http://www.nhgis.org/

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University websites

•Penn State’s PASDA

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International sites

Rwanda Ministry of Health

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International sites

USAID/PEPAR

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State agencies

Texas Department of State Health•http://www.dshs.state.tx.us/chs/

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Local agencies

•Engineering Companies-land surveys, aerial photos, CAD drawings

•Government agencies-Adelaide Australia Tip: search by “Adelaide Planning Department)-Austin, TX

Tip: Search by county name (Travis, County Texas)ftp://ftp.ci.austin.tx.us/GIS-Data/Regional/coa_gis.html

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Local agencies

Documents

GIS 1 Geographic Coordinates. GIS 2 Geographic Coordinate System Spherical coordinates based on angles of rotation of a radius anchored at earth’s center