Lab 3
Comparison of Image Perspectives, Scales, and Spectral
Bands
Geog 418/518, Fundamentals
of Remote Sensing
The goals of this lab are to:
a)
provide you a
brief introduction to using ERDAS Imagine for viewing images;
b)
have you use
think about some of the relative advantages and disadvantages of using
different image perspectives, image scales, and spectral resolutions; and
c)
challenge you to think about some applications for the
different image types.
This will probably be the shortest
lab of the quarter. Following labs are
significantly longer and will require more time to complete.
Lab Procedures:
I want you to work in pairs
on this lab and turn in only one lab per
team. Many studies and my own
personal experience have shown that working in pairs maximizes the amount of
learning that occurs. Even if you feel
you understand the materials perfectly, the act of discussing and explaining the
materials with your partner or comparing answers will improve your understanding
and your ability to articulate your knowledge to another user – a key skill in
remote sensing. As a remote sensing
professional, you will often find yourself in the position of having to explain
the imagery and the analysis to novices.
This is a good starting point for acquiring those verbal presentation
skills.
Your team is also encouraged
to talk to other teams if you get stuck.
You must, however, fill in the answers with your own words.
Write answers in complete
sentences, except where the question specifies otherwise. Please be legible.
Lab Activities and
Questions:
Make a folder in your private
data directory called Myname_Lab02. Then
go into the Geog418/Lab_02class folder and copy all the files to your Myname_lab02
folder. In ERDAS imagine, go to the menu
and specify under Session/Preferences that you want the Default Data Directory
and Default Output Directory to be the Myname_Lab02 folder.
You will now have a number of
image files in Myname_Lab02. These images
are:
·
Lamar_closeup_oblique, which is an closeup digital shot of the gravel flats along side the
·
Lamar_landscape_oblique, which is a panorama shot looking downstream (west)
from the bluff top that you can see in the closeup
shot. This is a .jpg image.
·
Lamar_1m_BW,
a 1 m pixel resolution aerial image of the
·
Lamar_1m_color,
a 1 m pixel resolution aerial image of the
·
Lamar_1m_TM5,
a 1 m pixel resolution 6 band (similar to the thematic mapper sensor on the
Landsat satellite) aerial
image taken on
·
Lamar_8m_color,
a 8 m pixel resolution color aerial image of the
·
Lamar_high_oblique, a Space Shuttle image looking off to the side. This is a .jpg image.
The table below summarizes
the characteristics of the images:
|
Image |
Perspective |
Spatial
Resolution |
Spectral characteristics |
|
|
Number of bands |
Spectral Coverage |
|||
|
Lamar_closeup_oblique |
Oblique |
~3 cm |
3 |
Visible: Red, Green, Blue |
|
Lamar_landscape_oblique |
Oblique |
~25 cm |
3 |
Visible: Red, Green, Blue |
|
Lamar_1m_BW |
Vertical |
1 m |
1 |
Visible: Gray tones |
|
Lamar_1m_color |
Vertical |
1m |
3 |
Visible: Red, Green, Blue |
|
Lamar_1m_TM5 |
Vertical |
1 |
6 |
Visible (Red, Green,
Blue) & 3 bands of NearIR |
|
Lamar_8m_color |
Vertical |
8 m |
3 |
Visible: Red, Green, Blue |
|
Lamar_high_oblique |
Oblique |
~500 m |
3 |
Visible: Red, Green, Blue |
You will open the images in
different viewing windows in ERDAS and compare them to one another. Note that you must specify that the images
are .jpg format for the Viewer window to “find” them.
As
you answer the questions below, provide a brief summary of:
1)
what information is gained
or lost as you use different perspectives:
2)
What information is gained
or lost as you use different spatial scales;
3)
what information is gained
or lost as you use different spectra to view the landscape; and
4)
what applications each image
might be used for.
Name 1
Name 2
1. What information is gained or lost as you use different
spatial scales?
a)
Finer resolution (large scale) imagery:
b)
Coarser resolution (small scale) imagery:
2.
What information is gained or
lost as you use:
a)
Oblique views?
b)
vertical perspectives?
3. Bring up the 1 m resolution black and
white, true color, and 6 band images in three different views. Visually compare what
features appear similar or dissimilar based purely on shades of gray or color. Then use the spectral profile tool to
compare the spectra of two or more features
(e.g., a tree tops, gravel, wood, water) on Lamar_1m_TM5 image (the
profiler tool will not work on the other two images, which do not have spectral
attribute data files associated with them). In the spaces below, discuss what
advantages/disadvantages might occur (e.g., what information is gained or lost) as you use
different spectra to view the landscape
a)
Black&White
b)
True color:
c)
False color infrared (using the Lamar_TM5_1m image, assign band 4 to red, band 3
to green, and band 2 to blue):
a)
3 and 25 cm, ground-based
oblique photos:
b)
Airborne black and white, 1 m
image.
c)
True color images, 1 and 8 m
resolution.
d)
6 band image, false color
composite, 1 m resolution.
e)
Oblique satellite imagery at
0.5 km resolution.