Images of Earth’s Surface

Images of Earth’s Surface

This image of volcanic mountains
was taken from a satellite in space,
using a sensor that detects light we
cannot see. It was enhanced on a
computer to make different
materials on the surface stand out.

How do we view large areas of Earth’s
surface?

By the end of this lesson, you should be able to
analyze images of Earth’s surface to identify land
features.

Directions

Work through each slide, listening to the videos and answering the questions.

As you read the story, annotate the reading, this means to highlight and drag and drop reading
codes to bring attention to different parts of the story as you read.

This is different then what I thought

I don’t understand

This is Important

I knew that

READING CODES:

Engage Your Brain

Directions: Fill in the table to compare the aerial photo with the satellite image. What things can be
seen or not seen in each image? In what other ways are they different? Can you think of reasons
that people might use each image?

Aerial Image
Satellite Image

Aerial Image

Satellite Image

● Taken from an

airplane

●

● Taken from space
●

What are some images of Earth
produced by remote sensing?

Before airplanes and other aircraft, observations of Earth
were made from the ground. Now, observations of Earth
can be made from the sky and from space using remote
sensing. Remote sensing is the process of gathering
and analyzing information about an object without
physical contact with the object. Remote-sensing
images of Earth are used to study things such as land
features, weather, and crop cover. These images are
also used to study and model changes, such as glacial
advances and retreats.

Some remote-sensing images, such as the one right ,
look the same as they would if you were viewing the
landscape with your own eyes.

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This aerial photograph shows a landscape
shaped by erosion in Bryce Canyon National
Park, Utah.

These images are made using data from sensors that
detect visible light. Visible light is one kind of
electromagnetic (EM) radiation, which is energy traveling
as electromagnetic waves. Some remote-sensing
images are made using data from sensors that detect
other kinds of EM radiation, such as infrared and
ultraviolet radiation. These types of EM radiation are
invisible to the human eye. To make images we can see,
computers are used to process the data collected by the
sensor

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READING CODES

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Describe Remote Sensing in your own
words:

Aerial Images

The first aerial photographs were taken from hot-air balloons in
1858. Today, aerial photographs are taken from aircraft such as
airplanes and helicopters. Some aerial images are produced with
sensors that detect both visible light and infrared light, such as the
color-infrared image on the left. Color-infrared images make
certain features stand out. Aerial images are used for scientific
investigations, land surveying, and many other purposes.

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Satellite Images

Satellites orbit Earth hundreds of kilometers above the planet. Satellites with many different types of sensors are
used to monitor Earth’s surface. Data gathered by the sensors can then be used to produce many different kinds
of images. Weather satellites, for example, can use sensors that detect visible and infrared radiation. The sensor
collects these data, then they are processed to produce images showing clouds, surface temperatures, and
many other variables related to weather.

Satellites equipped with radar use radio waves, another type of EM radiation, to gather data. Images made using
radar can show many different features. For example, radar images can show very slight height differences in the
ocean’s surface that reflect the shape of the sea floor below

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Interpret The large photo below shows one sand dune. Look at
the smaller satellite image at the bottom right of the photo.

About how many sand
dunes do you think the
satellite image shows?

What is GPS?

Theglobal positioning system, or GPS, is a network of
satellites orbiting Earth. A GPS device is a tool that can be used
from the ground or from Earth’s atmosphere. A GPS device
communicates with at least three GPS satellites at the same time.
The data the GPS device receives allow it to calculate its height
above sea level and its position on Earth. A GPS device can also
calculate speed and direction as the device moves.

GPS devices are used to navigate as well as to collect data.
Imagine you were collecting fossils and wanted to record where
you found each fossil. You could use a GPS device to record each
location. Some GPS devices also allow you to take photographs
and write notes. GPS data can be transferred to a computer to
view location points on a map. For example, the bottom map on
the next page shows points that represent the locations of geysers
in part of Yellowstone National Park.

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This GPS satellite communicates
with GPS devices on Earth.

As you read, underline and bold the
information a GPS device can calculate

What is GIS?

A geographic information system, known as GIS, is a program
used to view and make images and maps. GIS can be used
with many sources of information: different kinds of maps,
images, and data can be combined, or layered, using GIS.

GIS is useful for many applications and types of research. For
example, consider a team of biologists who want to study the
factors affecting the distribution of a particular plant. Using GIS,
the biologists could layer information to produce a map that they
could then analyze. They might start with a satellite image, then
add a topographic map layer, to show the land’s steepness and its
elevation. Other layers could be added that show roadways,
buildings, soil types, rainfall, or land use. These types of custom
made maps make it easier to analyze information about Earth’s
surface and identify relationships between different factors.

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READING CODES

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Which land features can you identify on the satellite
image?

Are any features easier to see on the topographic map?

What do you notice about the geysers and the vegetative
cover in the bottom image?

Zoom in and look at the
images, read the captions
and answer the questions.

What factors are considered when
interpreting images of Earth?
Aerial and satellite images have allowed scientists to study
Earth’s land features and natural processes in new ways. For
example, remote-sensing images allow scientists to study
large-scale land features and processes that would be difficult
or impossible to study from the ground.

Drawing conclusions from remote-sensing images requires
careful and informed interpretation. Many factors, such as the
level of detail shown in the image, the angle at which the
image was taken, and the type of sensor used, affect what a
remote-sensing image shows. Scientists must consider these
and other factors when interpreting remote-sensing images

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How has remote sensing affected the
way that scientists can study Earth’s
surface?

Level of Detail
Different remote-sensing images show the surface at different levels of detail. Think
about pictures of Earth’s surface that you have seen in newspapers or online. Some
show large areas, such as an entire mountain range, while others show smaller areas,
such as a single mountain. You might notice that some images look blurry, while others
look clearer and more detailed.

Aerial images are taken from lower heights than satellite images and generally give
greater detail than satellite images. Other factors also affect the level of detail visible in
an image. Imagine you are in an airplane. How would your view change if you were
looking through a pair of binoculars? Although you are in the same position above Earth,
the binoculars would help you see more detail. Similarly, different remote-sensing
technologies can affect the level of detail shown. The level of detail that will be most
useful depends on what a researcher is studying.

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Image Type

Remote-sensing devices can show information about Earth such as rock and mineral types, elevation, water
use, vegetation, temperature, and landforms. Infrared sensors, for example, can record temperature variations
on Earth’s surface. Then, a computer converts the data to colors we can see. The resulting image shows
temperature variations at different locations. Infrared images also make vegetated areas and rocky areas easier
to tell apart.

Technology called LiDAR, or “light detection and ranging” can show what Earth’s surface looks like beneath
dense vegetation. LiDAR systems send laser pulses to Earth’s surface. This gives information about the
elevation and shape of the vegetative cover and also of the solid ground below. See the images to the right.

Natural-color satellite images show colors close to what the human eye would see. Colors may also be added to
an image to display the information in a format that highlights the content of interest. The type of image selected
depends on the research topic.

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These three images all show the
same area.

1 This is a color aerial
photograph.

2 This LiDAR image shows the
plant cover.

3 This LiDAR image shows the
shape of ground below the
plants. A fault line runs between
the white arrows on the top and
bottom.

Viewing Angle

The angle the camera makes with the ground affects the image
produced. An image taken at an angle can show elevation
features that you may not be able to see in an image that is
looking straight down. The angle between the ground and the
camera also affects the appearance of distance between land
features on the resulting images. This type of distortion can
make accurate measurements difficult. Computer programs,
however, can partially correct viewing-angle distortions. The
angle between the sun and the camera affects the image, too. If
sunlight is entering at an angle, for example, it will cast shadows
on the land surface.

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The colors on this image

represent different types of
minerals that make up rock.

Why is it useful for this image to be shown at an angle, rather
than looking straight down?

What land features can remote sensing
show?

Remote-sensing images can help you identify land features that
are difficult to see from the ground. For example, standing on the
ground, you might see a long stretch of river that eventually
curves out of sight. In contrast, a satellite image could show the
entire river, from its beginning to where it runs into the ocean.
You could also see how the river connects with other streams
and rivers in a larger river system.

Remote-sensing images can show large erosional features such
as broad valleys or canyons. Large depositional features, such
as vast flood plains along river banks, can be seen using remote
sensing images, too. A fan-shaped region of deposited sediment,
called a delta, can be found where a river empties into an ocean
or a lake. These and many other land features are more easily
seen in remote-sensing images.

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As you read, underline and bold
examples of land features that
can be seen in remote-sensing
images.

Parts of this ash
flow are over 200
meters deep, about
the height of a
60-story building.

Valley of Ten Thousand Smokes,

Katmai National Park, Alaska

This satellite image shows the Valley of
Ten Thousand Smokes in Alaska. The
tan area is an ash flow from a 1912
volcanic eruption.

Describe two other land features that
you see.

Identify the erosional and depositional land
features in the satellite image. Read the
descriptions, then drag and drop brown the
names of the features in the yellow boxes.

Cliff: a steep, vertical, or
overhanging wall of rock

Alluvial Fan: a fan-shaped
deposit of sediment, found
where a stream enters flatter
land at the base of mountain

Canyon: a steep valley with cliff
walls, eroded by moving water

Cliff

Canyon

Alluvial Fan