1. Topic 2
A look at the Earth’s shape, coordinate systems, topographic maps, and data field analysis.

2. Measuring the Earth Earth is an OBLATE SPHEROID
Slightly flattened at the poles and bulged at the equator
Polar Diameter: 12,714 km
Equatorial Diameter: 12,756 km
Because of this, you actually weigh more at the poles

3. Proof of Earth’s Curved Surface
“Sinking Ships”
Gravitational Measurements
Photos from space
Altitude of Polaris increases as you move North

4. Locating Places on Earth
Latitude and Longitude

5. Locating places on Earth
Latitude
How many degrees above or below the Equator you are (either N or S)
These measurements are made in Degrees (º) and Minutes (‘)
1 degree = 60 minutes
Longitude
How many degrees east or west of the Prime Meridian you are (either E or W)
These measurements are also in Degrees and Minutes.

6. Latitude:
Lines of latitude are actually circles stepping north or south to pole points
Called “Parallels”
3 Rules:
1. Must be N or S of the Equator
2. Can’t be over 90 º
3. Numbers found on the SIDES of a map
Lines of Latitude

7. Finding your latitude using Polaris, the North Star
Does not “appear” to move because it’s directly above the geographic N-pole
The altitude of Polaris above the horizon equals your latitude (in degrees) on Earth

8. Altitude of Polaris (Latitude)

9. Longitude Measure angular distance E or W of the Prime Meridian
Called “Meridians”
3 Rules:
1. MUST always be E or W
2. NEVER over 180º
3. Number on the Top and Bottom of a map

10. Time zones are based on longitude
The earth is a sphere so there are 360 degrees going around it.
The earth rotates once in 24 hours cycling through that 360 degrees.
360o / 24 hrs= 15o / hour
Therefore for every hour you are away from prime meridian time (GMT) you are 15 degrees of longitude away from there.
If your time is earlier you’re West, later you’re East of the Prime Meridian.

11. Using Latitude and Longitude
Always give LATITUDE FIRST, then LONGITUDE
Ex. 30º N, 75 º W
Ex. 30 º 12’ N, 75 º 47’ W

12. New York State

13. A. Canary Island Hot Spot B. Yellowstone Hot Spot C. Iceland Hot Spot
Using Page 5 of your Reference Tables, What is the Latitude and Longitude of the following?
A. Canary Island Hot Spot
B. Yellowstone Hot Spot
C. Iceland Hot Spot
D. Sandwich Plate
E. Hawaii Hot Spot

14. Field: any region of space or the environment that has some measurable value or a given quantity at every point

15. Alternate Definition of a Field:
Any aspect of matter or energy that can be measured
Examples:
Gravity, magnetism, temperature, X-ray concentration, sound levels, elevation or depth, atmospheric pressure, wind speed, acidity of the atmosphere, relative humidity

16. Measuring the Fields you need to know.
Use isolines:
Def: Lines on maps used to represent areas of equal field value.
Examples:
Isobars-lines that connect areas of equal air pressure
Isotherms-lines that connect areas of equal temp.
Contour Lines -lines that connect areas of equal elevation on contour maps

17. NOTE: Equation is on page 1 of Earth Science Reference Tables
Gradient
The rate of change over distance within a field
Usually used with topographic maps, temperature maps and pressure maps.
Change in (amount of) field value
Gradient=
Change in distance
NOTE: Equation is on page 1 of Earth Science Reference Tables

18. Sample Gradient Problems:
1. If the elevation of Taos is 3,400 ft and the elevation of Phoenix is 1,000ft, find the gradient between them if they are 600 miles apart. 3,400’-1000’/600=4’/mi
2. If the temperature near the ceiling is 30 degrees C and the temperature near the floor is 22 degrees C, find the gradient if the distance between them is 12 feet. 30oC-22oC/12ft=0.67oC/foot

19. Getting Acquainted With Topographic Quadrangles
First things to do:
1. What SERIES map are you working with?
- series: shows you how much area
(Lat. & Long.) the map covers
-Ex: 15 minute (15’) series: Conesus
-Ex: 30 minute (30’) series: Chief Mt.
-Ex: 7.5 minute (7.5’)series: Livonia
*To determine Map Series:
Series = North Latitude – Southern Latitude

20. Getting Acquainted With Topographic Quadrangles
First things to do:
2. What is the CONTOUR INTERVAL on your quadrangle?
-Contour Interval: the number of feet
between contour lines; allows you to
determine elevation with your map
-Located at the BOTTOM CENTER of your quadrangle

21. Getting Acquainted With Topographic Quadrangles
First things to do:
3. What SCALE is your map drawn in?
-Scale: ratio of the distance on your map
to the actual distance on the Earth
3 Scale types:
1. Verbal: 1 inch = 62,500 inches
Therefore: 1” on map = 1 mile on Earth

22. Getting Acquainted With Topographic Quadrangles
Map scales con’t:
RF Scale
1:62,500
Land unit
Map unit
Must Be The SAME UNIT
Therefore: 1” on the map = 62,500” on the
Earth’s Surface
or 1” = 1 mile on Earth

23. Getting Acquainted With Topographic Quadrangles
Map scales con’t:
Graphical Scale:
the line at the bottom of your quadrangle divided into miles, feet, or kilometers
Can be used quite accurately to determine straight line distances or with a piece of string to determine curved distances
Ex: Conesus Quadrangle

24. Getting Acquainted With Topographic Quadrangles
First things to do:
4. How do you determine ELEVATION on a topographic quadrangle?
Elevation: Distance in feet above sea level
-Isolines (contour lines) connect points of equal elevation above sea level
-by using the contour interval and lines one can determine the elevation of features on the map

25. Getting Acquainted With Topographic Quadrangles
5. RULE OF V’S:
-contour lines always point upstream when they cross valleys forming a V-shape; thus water must flow the opposite direction.
-see next slide for example

27. Getting Acquainted With Topographic Quadrangles
6. Rule of DEPRESSIONS
-a depression contour line has hachure marks which indicate the direction in which the elevation decreases
-therefore; depression contours indicate a hole or bowl-shaped area. See “Fact Sheet” for more detail. 40 50

28. Getting Acquainted With Topographic Quadrangles
7. Index Contour Line:
- a darker contour line which has its elevation labeled
8. Bench Mark (BM):
- a point on the map which has actually had its elevation measured and recorded
-Ex: BM452

29. Getting Acquainted With Topographic Quadrangles
9. Profiles
-The side-view of an area’s landscape features
-allows for upward and downward changes of a line to be shown as changes in elevation or slope

30. Rules for creating profiles:
1. Find your contour interval
2. Find the profile line on the map which you are to draw
3. Place a slip of paper along the profile line and mark the edge of it every time it crosses a contour line
4. Label the marks with the value of each contour line they cross
5. The marks are projected onto a piece of lined paper (labeled according to the contour interval) and connected with a smooth curved line