Modeling the EarthTopic 2

Earth ScienceMs. Cooke2015-2016

Part 1 – What is a map?

• A map is a representation of an area or location on Earth.

• A map is a pf the Earth, or an object.• Parts of a Map:

– – – – –

• A is someone who makes maps.

The Coordinate System

• To locate places on the Earth, a grid system has been developed that assigns to numbers to each location.

• - The angular distance north or south of the Equator ( ). – Determined by the angle of the North Star

( ) above the horizon in the Northern Hemisphere.

– Angles of latitude are also called • Why?

Latitude

Angle of Polaris

• Latitude can be determined by fins=ding above the horizon.

Use and astrolabe to find angle.

Latitude

Hemispheres by Latitude

Longitude

• Longitude – Based on the apparent movement of the . (Time)

• Measures the Angular Distance or of the ( ).

• Angles of Longitude go from to . – –

Longitude

Hemispheres by Longitude

Hemispheres

Coordinate PracticeCoordinates Practice…

0o

15o

30o

45o

60o

Time Zones

• Time zones are based on

• Rules – –

• •

– If the time difference between New York City and London, England (0°) is 5 hours, What is the Longitude of NYC?

World Time Zones

US Time Zones

Coordinate Precision

• Every of latitude is of the Earth’s Circumference = .

• Each consist of (‘). – 1 minute = – Each consists of (“).

• 1 second =

Mapping Technology

• GPS – – Uses 29 satellites that transmit microwave

signals to receivers on the ground (GPS Unit).– GPS Information

• • • •

Mapping Technology

• GIS - technology and satellites have made it easier to integrate valuable information into very specialized maps.

• Anyone can access mountains of data (using the internet) to create maps of almost anything.

GIS Imagery

• GIS has almost infinite possibilities

• GIS changes the way we can view data and study problems

• Business, government agencies, scientists, & ordinary people are using GIS everyday.

» http://maps2.cattco.org/parcel/

Part 2Modeling the Earth in 3D

TOPOGRAPHC MAPS

Topography

• Topography – The shape of features of an object (such as the Earth)

Fields and Isolines

• A is a in which a similar quantity can be measured at every point or location.

• connect points of . on a field map (EVERY POINT ON THE LINE IS THE SAME)

• No isoline can ever cross… why? • Types

–

–

–

Topographic MapsTopographic Maps

• Two dimensional model of the Earth’s surface (represents 3-D world)

• Topographic maps are also known as contour maps.

• Contour lines – type of isoline used to show elevation, or height above sea level.

Contour Map

“Real World”

Index Contours & Contour IntervalsIndex Contours & Contour Intervals

• Index Contour –

Usually every 5th line is printed darker and has an elevation printed on it.

• Contour Interval –

the distance between each contour line.

Contour IntervalContour Interval

• Contour IntervalContour Interval –

difference in elevation between each line. MUST be equal spacing.

Contour interval =

20 feet520

540

560

580

Finding ElevationsFinding Elevations

• 11stst – Find the contour – Find the contour interval of the mapinterval of the map

• 22ndnd – Find the indec – Find the indec contours near the contours near the locationlocation

• 33rdrd – If the location id – If the location id on s line, you know on s line, you know the elevation. If it is the elevation. If it is between – estimate!between – estimate!

Contour Interval = 20 ft

Rules for Contours

1. Contour lines never cross

Rules for Contours

2. Contours form closed loops (even if not shown of the map.

Rules for Contours

3. Contours bend upstream (uphill) when crossing a stream.

Rules for Contours

4. The maximum possible elevation for a hill is “1” less than what the next contour “should” be.

The highest possible elevation of the hill is just below the value of  the next line that is not shown

5060

70

80

90

239

399

179

Rules for Contours

5. The lowest possible elevation for a depression is “1” more than what the next contour “should” be.

The lowest possible elevation of a depression is just above the value of  the next line that is not shown

50

90 90

80

7060

51

Rules for Contours

1. Contour lines never cross.

2. Contours form closed loops (even if not shown of the map.

3. Contours bend upstream (uphill) when crossing a stream.

4. The maximum possible elevation for a hill is “1” less than what the next contour “should” be.

5. The lowest possible elevation for a depression is “1” more than what the next contour “should” be.

SteepnessSteepness

• Steeper Slope (Gradient) – contour lines are closer together.

SteepnessSteepness

• Gradual/Gentle Slope (Gradient) – contour lines are farther apart.

SteepnessSteepness

• Steeper Slope (Gradient) – contour lines are closer together.

• Gradual/Gentle Slope (Gradient) – contour lines are farther apart.

A

B

Hills and Valleys

Hills have contour lines that form smaller and smaller concentric circular shapes towards a central point

Valleys are shown by the “V” shapes in the contour lines, between hills.

Depressions

• Contour lines which show a depression, crater, or sinkhole on a map.

• Drops in elevation towards a central point.• Shown by dashed lines (hachure marks) on the inside of

a contour line • The elevation of the first depression contour is the

same as the lowest regular contour near it.

Determining Direction

• Direction Is determined by the .– Often, the top of the map is

• - Due to the Earht’s magnetic field, a compass does not point

, instead it points to the .

Magnetic Declination

• On the map you will see –1. States the magnetic declination at

the time the map was made.

2. Varies by location and over time.

3. Today our magnetic declination is about 11 degrees.

4. What is the magnetic declination shown here?

Finding Distance

• Use the scale on the map to find the distance between two points.

Finding Distance…

Use the Scale on the map to find the distance between 2 points.

●

●

0 1 2 3 4 miles

Finding Distance

• Use the scale on the map to find the distance between two points.

Finding Distance…

Use the Scale on the map to find the distance between 2 points.

●

●

0 1 2 3 4 miles

Finding Distance

• Use the scale on the map to find the distance between two points.

Finding Distance…

Use the Scale on the map to find the distance between 2 points.

●

●

0 1 2 3 4 miles

Finding Distance

• Use the scale on the map to find the distance between two points.

Finding Distance…

Use the Scale on the map to find the distance between 2 points.

●

●

0 1 2 3 4 miles

Relief

• The difference in elevation between the highest and lowest points. – What is the relief?

Relief

• Calculate the relief between points A and B

Calculating Gradient or SlopeCalculating Gradient or Slope

• The slope between any two points on a hill

• Gradient = Change in Field Value

Distance

Calculating Gradient or SlopeCalculating Gradient or Slope

• Gradient = Change in Field ValueDistance

GradientGradient

• A trail is four miles long as measured by the scale on a map. The beginning of the trail is at the 1,060 ft contour line and the end of the trail is at the 960 ft contour line. Calculate the gradient of the trail.

Gradient = =1060 ft – 960 ft

4 miles25.0 ft/mi

Topographic Profile

• The side view