Unit 3: Mapping the Earth’s Surface
Royal Observatory at Greenwich, near London, marks the Prime
Meridian, where east meets west.
OBJECTIVES
• Introduce reference systems used for
locations on the Earth’s surface
• Describe the most important
characteristics of maps and the features
of common classes of map projections
• Interpret isoline maps.
• Discuss contemporary developments in
geographic information science
Locations on Earth
• Latitude-parallels
• Longitude-meridians
• Prime Meridian
• Great Circles
Latitude and Longitude
Global Positioning
System (GPS)
Provides location (lat, long) and
elevation using orbiting satellites
based on a corrected geoid (the
reference ellipsoid of the Earth). The
correction is made due to gravity
variations as shown on the maps
below.
Source: http://en.wikipedia.org/wiki/Geoid
GPS monitor on a tripod can be used to measure small
movements of the Earth from earthquakes, plate
tectonics. Source:
http://celebrating200years.noaa.gov/transformations/ht_mod/image6.html
In a remote area, the GPS provides accurate
location and elevation from 3 satellites.
Map Projections
• Cylindrical (A)
• Mercator (A)
• Conic (B)
• Planar
• Equal-area
The Mercator Projection
-Distortion greatest near the poles
-Provides true and constant compass
bearing-rhumb lines
Planar gnomic projection: meridians converge at
poles and straight lines follow great-circles
Equal-area projection preserves relative sizes
of continents;
Interrupted form-not continuous, thus
minimizes distortions
The Robinson map projection
• Compromise between area and shape distortion
• Shows whole globe; stretches poles into lines
Source: http://gothos.info/wp-content/uploads/2011/04/robinson.png
Isarithmic (isoline) map showing contours of equal values
(rainfall)
• Like topographic (height) charts, reduces 3-D volumetric data onto
2-D map.
Topographic contour
maps showing
horizontal map of
isolines (A) and vertical
cross-section of
traverse line XY (B).
Perspective
sketch of coastal
landscape (A) and
corresponding
topographic map
(B).
Geographic Information System (GIS)
• Computer-generated
overlays
• Query capabilitiescan ask questions of
data (ie, where will I
find the combined
features A-I-1?)
Remote Sensing
• Satellite based
• Aircraft based
• Ground based (radar, infrared)
Landsat image of the Los
Angeles area showing
vegetation (red), urban areas
(blue-gray) and water (black).
Vegetation mostly associated
with higher terrain, notably the
San Gabriel Mountains to the
north of the city and the Santa
Monica Mountains to the west.
Remote sensing of the environment
Active systems
Passive systems
Electromagnetic spectrum (wavelengths of energy)
Earth orbiting satellites gather data used in:
weather, climate, atmospheric pollution
geology, hydrology, soil science and agriculture, biology,
oceanography