Distance measure

Point A:

UTM Eastings = 450,000m; Northings = 4,500,000m

Point B:

UTM Eastings = 550,000m; Northings = 4,500,000m

State Plane Coordinate System

• Each state has one or more zones• Zones are either N-S or E-W oriented (except Alaska)• Each zone has separate coordinate system and appropriate projection

• Unit: feet no negative numbers

Map Projections for State Plane Coordinate System

N-S zones:

E-W zones:

SPCS• The origin for each zone is placed outside the zone to the

southwest (a false origin)

• X-origin:– Transverse Mercator (N-S) Zones 500,000 feet west of the

furthest point west– Lambert Conformal Conic (E-W) Zones 2,000,000 feet west

of the furthest point west

• Y-origin is not a specific distance to the south (varies by state and zone)

Use of SPCS

Advantages:• The system is used primarily for engineering applications e.g. utility companies, local governments to do accurate surveying of facilities network (sewers, power lines)• More accurate than UTM. SPCS deals with smaller area

Disadvantages: Lack of universality cause problems for mapping over large areas such as across zones and states

Data source

“Very few GIS projects have to start with no data at all. “

Data collected and made available by the various branches of government and third party vendors

Finding existing map data?

Data source in Davis Library

Data source in Davis Library

North Carolina • Center for Geographic Information and

Analysis

Florida • Florida Geographic Data Library (FGDL)

Government data providers

• U.S. Geological Survey

– Imagery, DEMs, DRGs, DLGs

• U.S. Census Bureau– TIGER

• National Oceanic & Atmospheric Agency– Coastal management

– Oil & chemical spills

– Coral reef conservation

• Natural Resource Conservation Service– STATSGO (U.S. General Soil Map)

Data from USGS

• Digital line graphs (DLGs)• Digital elevation model (DEMs)• Land use and land cover digital data• Digital cartographic text• Digital orthophotoquads (DOQ)• Digital raster graphics (DRG)

U.S. Geological SurveySatellite image

• http://edcimswww.cr.usgs.gov/pub/imswelcome/

US Census Bureau

TIGER/Line Files TIGER=Topologically Integrated Geographic Encoding and Referencing

US Census Bureau’s TIGER system automates the mapping and related geographic activities required to support the decennial census and sample survey program of the US census Bureau with the 1990 decennial census.

• First comprehensive GIS database at street level for the entire United States

Data Content of the TIGER/Line Files

Three major types: • Line features: roads, railroads, hydrography, and boundaries • Landmark features: (1) Point landmark: schools, churches etc. (2) area landmark: parks, cemeteries etc. • Polygon features: geographic entitiesNote: line and polygon features are the majority of data

Topology: provides the foundation for organizing spatial objects in the census TIGER data base.

Third Party Vendors

• ESRI

• TeleAtlas Map Databases

• DeLorme Street Atlas & Topo Usa

• GeoCommunity Data Bundles

Creating New Data

• Digitizing

• Scanning

• Field and Image data

– Digitizing• Transforms information from analog format

(e.g., paper, Mylar) digital format for computer storage & display

• Vector data capture

• Methods– Digitizing tablet – On screen digitizing using PC

Digitizing Tablet• Electronically active table surface

– Fine grid of wires acts as a Cartesian coordinate system

– Small & large formats available

http://www.calmit.unl.edu/geog412/Digitizing.pdf

Digitizing Tablet

• Puck– Connected to tablet– Records locations from map– Crosshair feature locator– Buttons indicate beginning/ending of

lines/polygons, left/right polygons

Also called “heads-up” digitizing

On-screen digitizing w/ PC

http://www.esri.com/news/arcnews/winter0102articles/epas-clean-water.html

Input devices: Scanners• Types:

– Desktop scanner – Drum scanners

“Drum scanner receives an entire sheet map, usually clamped to a rotating drum, and scans the map with very fine increments of distance.”

Raster Data Input: Remote Sensing

• Aerial photography– Source of base map data for many products check

products 1st

– Distortions caused by scale, relief, tilt

• Orthophotos/orthophotoquads– Type of aerial photo

• Corrected for scale, relief, tilt distortion• Available in analog & digital formats

• Satellite Imagery– Requires geometric & radiometric processing

• Geometric processing: GCPs

– Classification & accuracy assessment

GPS Data Input

• Supports development of highly accurate geodetic control

• Links field data collection to locations

• Cost & accuracy vary