1. 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!

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

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

4. 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

5. 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

6. 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

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

8. 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

9. Map Projections

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

11. Map Projections

12. 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.

13. Coordinate systems False origin Easting Northing
From:

14. 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)

15. Universal Transverse Mercator (UTM) Coordinate System

16. Universal Transverse Mercator (UTM) Coordinate System

17. 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

18. State Plane Coordinate System (SPCS)

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

20. 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):

21. 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

22. 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)

23. Virtual Globes Google Earth
Combining satellite, aerial and street level imagery: Over 20 petabytes (~20 million GB, ~20 billion MB).

24. El Paso County, CO geography

25. A Google Earth Primer