Today: Cartographic Basics –Map scale, datums, projections, coordinate systems Goals of Map Use Raster and Vector Lab Two – Google Earth / El Paso County

image from: Map Scale More “zoomed in” Less “zoomed in” Larger scale Smaller scale Larger fraction Smaller fraction

–1:1,000,000 example? –1:12,000 example? –1:1 example? –10:1 example? –1,000:1 example? Map Scale

To express map scale: 1.representational fraction such as 1:24,000 2.verbal scale “one cm to one kilometer” (1:100,000) “one inch to one mile” (1:63,360) 3.graphic scale bar Map Scale

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

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

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

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

Tangent: projection surface contact along one standard parallel only Secant: projection surface passes through earth touching two standard parallels Image from:

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 From: False origin Easting Northing

Coordinate systems Common coordinate systems in US: 1.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

Universal Transverse Mercator (UTM) Coordinate System

Coordinate systems Common coordinate systems in US: 2.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)

Coordinate systems Common coordinate systems in US: 3.The graticule – Latitude and longitude In Colorado Springs: 38 what? what?

Summary: Projections, coordinate systems, and datums determine how a GIS stores and displays spatial data. Knowledge of these topics is important in GES2050 (especially considering how many different sources of data we will assemble)

NEXT Goals of map use Raster / vector 21

GIS 22 Goals of map use Axes: 1. Audience (private to public) 2. Interaction (high to low) 3. Data relations (degree of certainty) Spheres represent typical uses of map MacEachren, A. M. and Kraak, M.-J Exploratory cartographic visualization: Advancing the agenda. Computers & Geosciences 23(4):

GIS 23 Are you a raster person or a vector person? Do you like Mozart or Beethoven? Do you like the Barry Manilow or Gorillaz? Do you like surfaces or networks?

Vector data model 24 (arcs) (nodes)

25 Vector data model

26 Vector data model

27 Vector data model

Topology structures are based on feature adjacency and feature connectivity. Topology is the method used to define spatial relationships. Without a topologic data structure in a vector based GIS, most data manipulation and analysis functions would not be practical or feasible. Arc / node topology 28 Vector data model TOPOLOGY: How vector data share geometry

Vector data model TOPOLOGY: How vector data share geometry 29

Vector data model TOPOLOGY: How vector data share geometry 30 B A

Vector data model TOPOLOGY: How vector data share geometry 31

32 Raster data model

33 Raster data model

34 Raster data model

35 Raster and vector

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38 NASA’s Earth Observing-1 satellite caught this image of the Guiberson fire by using shortwave IR to increase contrast between burned and unburned. 9/29/09 (Ventura County, CA) Why convert raster to vector?

39 Why convert vector to raster?

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 query

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 – How much data? – Combining satellite, aerial and street level imagery: Over 20 petabytes (approx. 21 million gigabytes, or 20,500 terabytes).

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