Contour Mapping

Topographic Maps – a detailed map showing hills, valleys, and other features of a specific area.

Vocabulary

Contour line – a line that connects points of equal elevation.

Contour Intervals – the difference in elevation between contour lines.

Index Contours – contour lines marked by a number (elevation)

Depressions Contours – lines that show dips or depressions in the land.

Map Legends – explains what symbols represent on a map.

Example:

Map Scale – the ratio between the distance on the map and the actual distance on the surface of the

Earth. There are three main types of scales:

 Verbal Scales – written in words“one centimeter equals one kilometer” 

 Graphic Scales – drawn on a line  Fractional Scales - written as a fraction

1:62,000 1/62,000

Gradient

The gradient or slope represents how steep the land is between two points.

Gradient = change in field value

distance

Topographic Profile

A topographic profile is a “side-view” of a topographic map along one line. A profile helps us see how steep or gentle a slope may be.

Remote Sensing

•Most maps have been made by collecting data on-site, but recently technology has allowed maps to be made from data collected at great distances.•The process of collecting data about the Earth from far above the Earth’s surface is called remote sensing.•Satellites will do most of the remote sensing of the Earth.

How do satellites collect data?

The Electromagnetic Spectrum 

• Energy is received and transmitted from the Earth through electromagnetic waves (light).

• Different types of waves have different properties, such as different wavelengths and frequencies.

Types of electromagnetic radiation:

Radio wavesMicrowavesInfrared radiationVisible lightUltraviolet radiationX-raysGamma rays

Wave Characteristics All electromagnetic waves travel at 300,000 km/s in a

vacuum (the speed of light)       Wavelength – the distance between waves (meters)

…from peak to trough.  

      Frequency – the number of waves that pass a particular point each second.

 

Landsat Satellites

• Receives reflected wavelengths of energy emitted from the Earth’s surface.

• Features of the Earth’s surface give off different wavelengths of radiation (different temperatures)

• Uses a moving mirror to scan the Earth.

Topex/Poseidon Satellite

• Maps the ocean floor by measuring the difference in high frequency signals that bounce off the ocean surface and reach the satellite.

• The ocean water will build-up in shallow areas and sink down in deep areas.

Sea Beam

• Maps the ocean floor using sound waves (sonar).

• A computer calculates the distance based on how fast the sound echo returns to the ship.

• This technology uses the speed of sound in water to calculate the distance to the ocean floor. (note: sounds is faster in water)

Global Positioning System (GPS)

• Radio waves from satellites can pinpoint your location (latitude & longitude), elevation, and speed.