GEOG 372: Introduction to Remote Sensing
Fall 2007
Laboratory 8
Analyzing Thermal IR Signatures
No
late labs can be accepted. Please
type the answers just below the
questions and hand the printouts at
the beginning of the next lab:
October 31st (0102) and Nov 1st
(0101).
Also
do not forget to mention your
MAJOR
on
your labs
The purpose of this
laboratory exercise is to gain some experience with understanding
thermal remotely sensed data and learn additional ENVI functions.
This lab is based on
the analysis of an ASTER (Advanced
Spaceborne Thermal Emission and Reflection Radiometer) image. ASTER is
an imaging instrument on board the Terra satellite launched in December
1999 as part of NASA's Earth Observing System. ASTER is being used to
obtain detailed maps of land surface temperature, reflectance, and
elevation <http://asterweb.jpl.nasa.gov/>
Open ENVI 4.2 and go
to File - Open Image File.
Navigate to U:\\g372\372-fall07\lab8data
and open AST_L1B_00304102003033845_06122003113158.hdf. You will
notice three files associated with the same image in this folder. Only
one of them is the actual image and the other two contain “header”
information and “metadata” which are used by the software to properly
read the data. Select the HDF file type. You will
see several stacks of bands open in the “Available Bands” window.
Examine the map info and other information found in the “Available
Bands” window and answer the following questions:
Note: The five thermal (TIR) bands and
their spatial resolutions have been mislabelled as SWIR bands with 30 m
resolution. These (TIR) bands have a spatial resolution of 90 m.
1. How many visible/NIR
bands are there and what are they (e.g. ultra violet, blue, green, red,
etc.)?
2. How many thermal IR
bands are there?
3. What is the
difference in spatial resolution between the visible and thermal bands?
Load bands 3N, 2 and 1 into the RGB
combination on Display 1.
4. Is it a true or a
false color composite? How do you know?
Load band 8 (2.3360µm) into Display 2.
Re-stretch the display settings to better see the bright spots in band
8. In Display 2 Image window go to Enhance – [Scroll]Linear.
In the pop-up The display now looks much darker with a few lighter
spots.
5. What are the lightest
and the darkest features in the thermal image now?
Use geographic link to link the two displays
together. Using the pixel locator for the thermal band, locate the
following pixels, and find the value of these pixels using
the “Cursor location/value” tool.
6. What do you think the features are that
contain these pixels?
a)
1128, 84
b)
2295, 771
c)
638, 1956
7. What can you see in
the corresponding areas of the visible image?
8. Which band should be
used for fire detection?
In the Image window of Display 2 (Band 8) go
to Overlay – Density slice. In the “Density slice band
choice” window select Band 8 (2.3360). In the “Density Slice” window, go
to Options – Set Number of Default Ranges and select 5
ranges. Go to Options – Apply default ranges, and then
Apply. Now look at the display. All the values in the
display have been color-coded based on the assigned ranges of values.
9. What range do the
majority of values fall under?
In the “Density Slice” window click on
Clear Ranges. Go to Options – Add new ranges.
In the pop-up window select 1 range starting with “red” for a color and
define the range 7 as minimum and 11 as maximum. Click Apply. Examine
the areas surrounding the three pixels mentioned earlier.
10. Is all active
burning found in the 7 – 11 range?
Using “Cursor location/Value” tool and “Edit
Range” button in
the “Density slice” window determine the range which will include all
the active burning in those three areas.
11. What is the range
that includes all active burning in the three areas?
12. What other features
fall within this value range?
13. Modifying the range limits
through the “Edit
Range” button,
determine the maximum range which includes active burning but excludes
other features. What is the range?
Take a screen shot of the final range displayed
in your Image window. The screen shot should include the zoom window
centered on pixel (2296, 763). Include the screenshot with your lab
write-up.
Copy your screenshots to a CD or USB jump drive,
email them to yourself, or print them using your print account.
Log off your
computer and turn off the monitor when you are finished.
Typed answers
with screenshots are due October 31st (0102) and Nov 1st (0101), 2007