1. Chapter 3: Models of the Earth

2. 3-1:Finding locations on the Earth
System of lines (longitude and latitude), divided into units of:
Degrees- 360 (divided) around the earth in any direction
Minutes- 60 minutes in each degree
Seconds- 60 seconds in a minute

3. Latitude- angular distance north or south of the equator (lines run East-West)
Called parallels because lines never intersect
Equator is 0°
North pole is 90°N
South pole is 90°S
Maximum measurement of 90° N or S

4. Longitude- lines that run north and south and intersect at the north and south poles, designated as E or W (except for 0 and 180)
i. Prime Meridian- 0°, runs through
Greenwich, UK (England)
ii. International Dateline- 180° E or W runs
through the pacific ocean
iii. Maximum Measurement of 180°

5. Finding direction
Using a magnetic compass- Earth has magnetic properties and a magnet will align itself with these poles
Magnetic pole are slightly different than longitudinal north
the difference between longitudinal north and magnetic north is called “magnetic deviation” or magnetic variation”
in the northern hemisphere, measured in degrees east or west of the geographic north pole
magnetic declination is very important in Navigation

6. Great Circles- any circle that divides the globe in half
used in navigation to find the shortest distance between two points on Earth
can run in any direction
GPS navigation
24 satellites use triangulation to determine position of receiver
location of satellites is known, your location is based on time the signal travels

7. Ch 3-2: Mapping the Earth’s Surface
Cartography- the science of map making
Cartographers use a variety of tools
field survey- cartographers walk and area and take precise measurements
remote sensors- satellites, airplanes used to obtain images of Earth’s surface

8. Map projections- round earth, flat maps, no problem. Well, sort of…
A map projection is a flat representation of Earth’s round surface
Cylindrical projection- (Mercator) cylinder wrapped around the globe
both latitude and longitude appear parallel
area around the poles is distorted
Better for small map areas

9. Azimuthal Projections- plane laid on top of globe
usually used at poles
distortion occurs equally in all directions
good for finding great circle routes in navigation

10. Conical projections- cone placed on globe touching one parallel of latitude
least distortion occurs where paper “touches” the globe
Polyconic (meaning “many cones”) produces a map with little distortion

11. Reading a map
Direction on a map
typically, north is the top of the map
to be sure, locate the compass rose/ single arrow to indicate north
Symbols
maps often use symbols to represent features
Symbols are explained in a map legend

12. Scale
The scale of the map indicates the relationship between the distance shown on the map and actual distance
Can be expressed in
Graphic Scale- a printed line that has marking similar to a ruler
Fractional scale- (ratio) 1 unit of distance on map equals “x” units on earth
verbal scale- a sentence that expresses scale

13. Isograms- a line on a map that represents an equal value of a given quality
“iso” means equal
“gram” means drawing
“gram” can be dropped and other words added, for instance
isobar- lines of equal air pressure
isotherm- lines of equal temperature
can be used to plot any type of measurement
isograms can never intersect (cross)

14. Section 3:Types of Maps
Infinite number of types of maps, many combinations
Photos- while you may not think of a photo as a map, it is a model of an area
Advantages
easy to visualize an Area
think “Google Earth”
Disadvantages
Distortion: objects appear small in the distance
resolution: the larger the area the less the detail

15. Shaded Relief map-
Advantages
can combine features of an area
provides information about physical features
can show larger areas than topographic map
Disadvantages
physical features are not in detail
does not show precise elevations, except in a few locations

16. Road map- created by cylindrical projection of small areas or GPS coordinates and remote sensing
Advantages
familiar to most
provides little distortion of small areas
Disadvantages
cannot show large areas in great detail without becoming to large to handle
occasionally difficult to read for some
not useful in remote areas where there are no roads

17. Topographic maps- show in detail varying elevations of an area using “contour lines”
Advantages
show precise elevation of the land
useful for hikers and military
Disadvantages
can be confusing
can only show small areas without becoming to large

18. Digital Elevation model
Advantages
shows proportion in usable way
easy to visualize perspective
Disadvantages
tall items in foreground block objects in the distance
difficult to show other features