20 points
Due: Monday, March 12, 11:59 pm (on Blackboard)
GPH 370 Module 6: Fundamentals of Remote Sensing
Goals
By the time you've completed this module, you will:

Be able to explain some basic remote sensing concepts, and the characteristics of several
multispectral scanners

Have an experience with visual analysis of remotely-sensed imagery

Have an introduction to digital analysis of remotely-sensed imagery. Specifically, you’ll
understand the logic of identifying earth features using spectral signatures.
Deliverables, and necessary resources to complete module
Your module 5 write-up should include:
 Part I – answers to all questions (7 pts)
 Part II: Answers to all questions (7 pts)
 Part III: A table, filled in as described in the instructions (6 pts)
To carry out the module, you’ll want the following resources available:

A computer with internet access, and Google Earth installed
Part I: Remote sensing concepts and sensors
(2 points ea. question except #2 which is 1 pt)
Use lecture material, your textbook, and internet research to answer the following questions in your
module 6 write-up: Brief responses are fine – two or three sentences or phrases for each question.
In your write-up, include the answers to each question, labeled with the question number. Some
questions include several parts – be sure to answer them all.
1. Briefly define each of the following terms:
 Spatial resolution
 Spectral range
 Spectral resolution
 Temporal resolution
2. According to the lecture, what is highest spatial resolution provided by aerial
photos? Now, open Google Earth, and use the “Fly to” option (see right) to go
to the intersection of Mill Ave. & University Dr in Tempe. Zoom in to one of
the nearby parking lots until you can see as much detail as possible of
individual cars. What would you estimate to be the spatial resolution of this
imagery?
3. In what country were the SPOT earth observation satellites developed? What is the spectral
range of SPOT’s bands, from the shortest to longest wavelengths detected? Is this greater or
less than that of LANDSAT 7’s? What is the spatial resolution of SPOT’s highest-resolution
imagery? (see note on next page)
(When you research SPOT, you’ll see that the range & resolution has changed from one satellite
to the next. For your module, choose one specific satellite – for example SPOT 5 or SPOT 6 – and
in your write-up note the satellite number as well as its range and resolution.)
4. What is GeoEye-1? Is it governmental/public or commercial? What is its maximum spatial
resolution, and which sensor provides this resolution? What is the spectral range of its bands,
from the shortest to longest wavelengths? What is its temporal resolution (also known as
revisit time)?
Part II: Visual image interpretation using Google Earth
(2 pts ea question except #3 which is 3 pts)
In this section, you’ll do some image interpretation, looking at several locations and interpreting the
imagery available in Google Earth.
The first two locations are fairly easy to recognize, and the last one is a little more challenging. For all 3,
be conscious of the recognition clues you’re using. Here’s the list illustrated in class, plus a couple of
additional ones:

Shape: Straight edges are usually man-made; irregular are usually natural. Transport: tight
curve is slower road, wide curve is faster

Size: Compare the size of an ambiguous feature with other features that you recognize

Shadow: Can suggest the height of a feature, and may reveal the feature’s shape when the sun
angle is low.

Tone/Color: For soil, darker means wet, lighter means dry.

Texture: Rough textures (like a forest) appear mottled. Smooth textures (like a field) have little
tonal variation.

Pattern: How are repeated elements spaced – random or regular?

Association: If you recognize some of the features that you see – what else is likely to be
around them? Barns are near farms; Transmission lines are near powerplants. Schools are near
playing fields – etc.!

Site: What is the location you’re looking at? What are you likely to kind in that location?
Use Google Earth’s “Fly to” search to find each of these locations. You’ll want to zoom in or out to get a
good look. Then answer the questions about each location.
1. Cator Stadium, Port-Au-Prince, Haiti
a. In the lower-left corner, of the image, below the bar scale, is a note giving a month, day
and year. This is when the image was recorded. What is the date of this image?
b. Just to the right of the date, you’ll see a small image of a clock, with a year to the right
of it (like at right). Click on the year, and a timeline will appear in the upper-left
corner (See example at right). Move the slider
bar close to the most recent date, until you see
some irregularly-shaped objects on the stadium
field. What do you think these are?
c. Now, think about how you interpreted what you saw. Which elements from the list
above helped you? In a sentence or two, explain what characteristics of shape, size,
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etc. helped you identify the objects. Be sure to mention the element, and what you
saw. For example, “I knew this was an agricultural area (site); and because the texture
was smooth, I knew it was a field, not an orchard.”
2. 44.275°, -123.253°, south of Monroe, Oregon
This location is described in decimal degrees. To go to it, you’ll need
to switch Google Earth to using decimal degree units. From the top
menu bar, choose Tools > Options (on a PC) or Google Earth >
Preferences (on a Mac), and on the “3D View” tab, choose Decimal
Degrees.
a. Once Google Earth takes you to this location, zoom in to it
so you can see it clearly. Be sure you’re looking at the most current imagery. What do
you think is grown in this particular field?
b. As for the previous location, explain what characteristics of shape, size, etc. helped
you identify the type of crop in this field.
3. Casper, Wyoming (30 km --- 0.5 km elevations)
Zoom out and pan to the north, south, east and west to get an idea of the extent of this town.
Casper has a variety of economic activities. Zoom in to a few areas until you’re pretty sure you
can identify two of the town’s economic activities.
a. Name the two activities.
b. For each one, explain what visual clues helped you identify them.
Part III: Image interpretation using spectral signatures (reflectance estimates 4 pts, uses 2 pts)
Although you’ll interpret images visually in this section, the exercise introduces the logic of digital image
interpretation.
For the sample image, you’ll estimate the amount of reflectance at several locations and for several
spectral bands, and use a spectral reflectance graph to make a hypothesis about what you’re seeing in
the image.
If you need a review of spectral signatures and spectral reflectance graphs, see the February 29 lecture.
To carry out the exercise, go to http://www.public.asu.edu/~aoblt/370/mod6/. This link is also
available under “Modules” in Blackboard.
1. You will see three black-and-white images of an experimental crop field in Kansas. Each image
shows the same area, but represents the reflectance from a different spectral range. Some
reminders:

Bright areas of the image have a high reflectance.

A completely WHITE area reflects ALL the energy for the particular spectral range. (For
example, if an area is white on the image labeled “green”, that area reflects ALL the
wavelengths 0.5-0.58 m range. In a color image, it would look very green.

A completely BLACK area ABSORBS all the energy for the particular spectral range., and
reflects NONE of those wavelengths.
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2. On the image at right, 5 circled
locations are labeled A - E. Using the 3
images on the web, estimate the
relative reflectance for each of the 5
points. Remember,

“0%” means “no reflectance”
and will look very dark

“100%” means “very high
reflectance” and will look
white.
3. Record your estimates on a table like the one below. Reflectances for point C have already
been completed.
Spectral reflectance table
Point
Green
Band
Red
Crop/Land Use
Near IR
90%
90%
90%
A
B
C
building
D
E
4. Now use the spectral reflectance graph below, and the values in your spectral reflectance
table, to make your best guess at the crop type in locations A, B, D and E. Enter your guess in
the right-hand column (“Crop/Land Use”).
(The web page with the
3 images also includes
a color version of this
graph, which may be
easier to interpret.)
5. Your write-up for Part III of the module will consist of the table above, with all the blank cells
filled in. If you like, you can copy and paste the table from the web page into your write-up, so
you don’t have to create it from scratch.
-- That’s all! --4