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GIS Lecture 5 Importing Spatial and Attribute Data

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Outline

•GIS Data Sets•Map Projections•Coordinate Systems•GIS Data Sources

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GIS Data Sets

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GIS Data Sets

• ArcInfo Coverages• ArcView Shapefiles• CAD Files• Aerial Photos• Event Files

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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 in ArcMap

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Polygon Coverages•Area and perimeter automatically calculated

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Polygon CoveragesPolygons share borders

B

A

D

1 2

3 4

Pine St.

Oak St.

734C

E

G

F733

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Line Coverages

•Length automatically calculated

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Point Coverages

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ArcInfo Coverages

•Advantages-Many feature types-Shared borders-Automatic Area/Perimeter/Length fields

•Disadvantages-Cannot edit in ArcMap

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ArcInfo Export files•.e00 export exchange file•ArcCatalog translates into ArcGIS•Creates coverages

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ArcView Shape Files

Advantages•heads-up digitizing and editing•less storage/rapid display •can export to CAD

Disadvantages•one feature type•no area or perimeter with new shapefiles

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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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CAD Files Why CAD Drawings?

• Better Precision for Digitizing -.DWG / .DXF

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Adding CAD Files

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CAD Files in ArcMap

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Aerial Images

Combining Grid and Vector Maps

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Event FilesX,Y Coordinates

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Event Files

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Event Files

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Map Projections

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Map Projections and Distortion

Map projections produce distortion in one or more spatial properties:•Shape, area, distance, and direction•Specific projections eliminate or minimize distortion

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Distortion Examples

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Mercator Projection: Distortion

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Robinson Projection: Distortion

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Projection Important•Measurements used to make important decisions•Comparing shapes, areas, distances, or directions of map features

•Feature and image themes are aligned

Los Angeles

New York

Los Angeles

New York

Projection: MercatorDistance: 3,124.67 miles

Projection: Albers Equal AreaDistance: 2,455.03 miles

Actual distance: 2,451 miles

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Projection not Important Business applications

•Not of critical importance. •Concerned with the relative location of different features

On large scale maps - street maps•Distortion may be negligible •Map covers only a small part of the Earth's surface.

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Coordinate Systems

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Coordinate Systems

•Spherical/Polar-Geographic Coordinate System

• Rectangular-State Plane-UTM

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Geographic Coordinate System

• Latitude and Longitude• Census Bureau TIGER files

Geographic Coordinate System Grid

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Longitude: Meridians

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Latitude: Parallels

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Origin° Longitude (prime meridian)0

° Latitude (equator)0

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Coordinates

Pittsburgh

-80

40

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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°

Pittsburgh’s Point

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World circumference through

the poles is 24,859.82 miles,

so for latitude:

1° = 24,859.82/360 = 69.1 miles

1’ = 24,859.82/(360*60) = 1.15 miles

1” = 24,859.82*5,280/(360*3600) = 101 feet

Length of the equator is 24,901.55 miles

Translated to Distance

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Rectangular Coordinate Systems

State Plane Coordinates- Local Governments

UTM- US Military

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State Plane Coordinate System

•Established by the U.S. Coast and Geodetic Survey (now the National Ocean Survey)

•At least one for each state•Rectangular (x,y) coordinates•125 zones, following state and county boundaries each with its own projection:

Lambert conformal projection for zones with east-west extent

Transverse Mercator projection for zones with north-south extent

•Cannot have zones joined to make larger regions

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Rectangular Coordinates

200

400

0 200 4000

(100, 200)

(400, 300)

East (Feet)

No

rth

(F

eet)

Has all positive Cartesian coordinates in feet, called false eastings and false northings

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State Plane Coordinate Zones

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State Plane Coordinate Zones

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City of Pittsburgh as Geographic Coordinates

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City of Pittsburgh as State Plane Coordinates

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State Plane Coordinate Names

•North American Datum of 1927 (NAD27)

•American Datum of 1983 (NAD83)

•"High Accuracy Reference Network" (HARN)

•"High Precision GPS Network" (HPGN)

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•Developed by the NATO in 1947

•Military grid system

•Based on transverse Mercator projection

•Applied to maps of the Earth's surface extending from the Equator to 84 Degrees north and 80 degrees south latitudes

Universal Transverse Mercator System (UTM)

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UTM Zones

World is divided into 60 north-south zones, each covering a strip 6° wide in longitude

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UTM Zones in the Contiguous USA

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Data Sources

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Other Sources of GIS Data

•US Census•ESRI Web Sites and Media Kit•Local Agencies•Land Surveys •Satellite Remote Sensing•Existing Paper Maps•Other WEB Sites

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US Census

• www.census.gov

- TIGER Maps

- Summary File(SF) Tables

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Census Tracts (TIGER)

Small, relatively permanent statistical subdivisions of counties

•delineated by local committees in accordance with Census Bureau guidelines

•between 1,000 and 8,000 people (in general)•1,700 housing units or 4,000 people•homogeneous population characteristics (economic status and living conditions)

• normally follow visible features•may follow governmental unit boundaries and other non visible features

• more than 60,000 census tracts in Census 2000

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State Census Tracts

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County Census Tracts

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City Census Tracts

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Census Blocks Groups

Block groups (BGs) are the next level below census tracts in the geo-graphic hierarchy

- a subdivision of a census tract

-400 housing units, with a minimum of 250, and a maximum of 550 housing units

-follow clearly visible features, such as roads, rivers, and railroads.

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Census Block Groups

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Census Blocks

Smallest geographic area for which the Census Bureau collects and tabulates decennial census information.

Block boundaries are visible (street, road, stream, shoreline, etc.) or nonvisible (county line, city limit, property line, etc.) features.

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Census Blocks

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Other Census TIGER Layers

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Summary File (SF) Tables American Factfinder

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SF1 Tables

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SF2 Tables

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SF3 Tables

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ESRI’s Website

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Data Sources

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ESRI Media Kit

•Data and Maps•8 CDs and DVDs-Data & Maps and StreetMap USA (DVD)-Image Data (DVD)-Global Imagery (DVD)-World, Europe, Canada, and Mexico (CD)-United States (CD)

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Local GIS Departments

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Local GIS Departments

• Chicago, IL- http://egov.cityofchicago.org/

• Austin, TX- http://www.ci.austin.tx.us/development/

• Tip: Search by county name (Travis, County Texas)

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GIS Consulting Firms

•Specifies boundaries, rights-of-way, and other legal descriptions

•Surveyors use optical and electronic instruments to measure precise control point locations established by geodesists

•High quality data, but takes a lot of time

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Existing Paper Maps

•Vector Digitizing•Raster Scanning

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GIS Servers

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Geography Network

www.geographynetwork.com

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Geography Network

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Penn State (PASDA) http://www.pasda.psu.edu/

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Penn State (PASDA)

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Penn State (PASDA)

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Ivan Flood Maps

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Summary

•GIS Data Sets•Map Projections•Coordinate Systems•GIS Data Sources