Today: Cartographic Basics Virtual Globes Google Earth demo (at PCs) Map scale, datums, projections, coordinate systems Virtual Globes Google Earth demo (at PCs) Lab Two – Google Earth: Finding Variety / Contrast in El Paso County, CO If time permits, beautify your website!

Map Scale More “zoomed in” Less “zoomed in” Larger scale Smaller scale Larger fraction Smaller fraction image from: http://rockyweb.cr.usgs.gov/outreach

Map Scale 1:1,000,000 example? 1:12,000 example? 1:1 example?

Map Scale To express map scale: representational fraction verbal scale such as 1:24,000 verbal scale “one cm to one kilometer” (1:100,000) “one inch to one mile” (1:63,360) graphic scale bar

Datums Datum: an imaginary surface to which ground control measures are referred. “Datums define the size and shape of the earth and the origin and orientation of the coordinate systems used to map the earth.” - Peter Dana But first: What is the shape of the earth? oblate spheroid

Datums There are hundreds of datums + 250 other variations Earth’s axis (m) Datum 6,378,137 World Geodetic System 1984 6,378,135 World Geodetic System 1972 6,378,160 Australian Datum 1966 South American Datum 1969 6,378,245 Pulkovo Datum 1942 6,378,388 European Datum 1950 6,378,206 North American Datum 1927 6,377,397 German DHDN + 250 other variations

Map Projections Purpose: to transfer info. from an oblate spheroid to a flat surface

Some distortion always results from the projection process: Map Projections Some distortion always results from the projection process: Distorted scale Distorted area Distorted distance Distorted shape Distorted relative size Distorted direction

Map Projections

Map Projections Tangent: projection surface contact along one standard parallel only Secant: projection surface passes through earth touching two standard parallels Image from: http://standards.iso.org/ittf/PubliclyAvailable

Map Projections

Coordinate systems While map projections define how positions on the Earth’s curved surface are transformed onto a flat surface; coordinate systems superimpose a grid onto the projected surface (datum) to provide a referencing framework to measure location.

Coordinate systems False origin Easting Northing From: http://gis.washington.edu/esrm250/lessons/projection/

Coordinate systems Common coordinate systems in US: Universal Transverse Mercator (UTM) Most common in US/Canadian mapping programs Used by Army since ~1947 Used by USGS since ~1967 Long. zone #s designate 6 deg. strips from 80S to 84N Lat. zones are 8 deg. S to N, labeled C to X Lower 48 in 10 long. zones In N Hemisph., northing origin is Equator In S Hemisph., northing origin is 10,000,000 at Equator Easting (at 500,000 meters) is the center of zone UTM shown on every 1:24K (1 km grid)

Universal Transverse Mercator (UTM) Coordinate System http://www.colorado.edu/geography/gcraft/notes/coordsys/coordsys_f.html

Universal Transverse Mercator (UTM) Coordinate System http://faculty.unlv.edu/jensen/CEE_468/img/UTM-NV.jpg

Coordinate systems Common coordinate systems in US: State Plane Coordinate Systems (SPCS) Developed by Coast Guard in 1930s For state and county level mapping 120 zones through states Ignores earth curvature Generally follows county boundaries Northing and easting such that no neg. numbers Problems: feet/meters, uses different coordinate systems for each zone, uses 3 different projections

State Plane Coordinate System (SPCS) http://www.ncdot.org/doh/PRECONSTRUCT/highway/location/support/Support_Files/Library_doc/graphics/1099figure3.gif

Coordinate systems Common coordinate systems in US: The graticule – Latitude and longitude In Colorado Springs: 38 what? - 104 what?

Summary: Datums, projections, and coordinate systems determine how a GIS stores and displays spatial data. Knowledge of these cartographic components is important in GES2050 (especially considering how many different sources of data we will assemble) MORE HERE (the Geographer’s Craft): http://www.pdana.com/PHDWWW.html

Virtual Globes A Virtual Globe (VG) seamlessly provides 3D maps of Earth (etc.) at various perspectives and scales; equipped with different themes (terrain, satellite, boundaries, roads, rivers, buildings). Supports geospatial query Supports sharing: Your GIS / spatial analysis results Your landscape perspectives / scenes Your animations and tours

Virtual Globes Geoid (Cornell, 1995) Encarta (Microsoft, 1997) SkylineGlobe (Skyline Software, 1998) TerraFly (Fl. Int’l Univ/NASA/IBM, 2001) Earth3D (2004) EarthBrowser (2004) World Wind (NASA, 2004) Google Earth (Google, 2005) CitySurf Globe (Turkey, 2006) Marble (2006) ArcGIS Explorer (2007) WorldView (2008)

Virtual Globes Google Earth Combining satellite, aerial and street level imagery: Over 20 petabytes (~20 million GB, ~20 billion MB). http://mashable.com/2012/08/22/

El Paso County, CO geography

A Google Earth Primer