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					Lab Instructions
Lab 8, due 8:00 am Nov 11, 2006
EES5053: Remote Sensing, Earth and Environmental Science, UTSA

Student Name: ___________________



               Calculate Temperature from ETM+ Image

Purpose

   In this lab, you will use IDL to compute the temperature of Landsat
image in the urban area of San Antonio, and analyze the distribution of
temperature.

1. Preparation:
   (1). Create your own folders:
       c:\EES5053\studentname\Lab7, storing your work and final lab report.

   (2). Connect to the server
      \\129.115.25.240\XIE_misc\EES5053\Lab8
   and copy the files in lab8 to your local computer.

   (3). Setup the ENVI data and output directory as local computer
   C:/…./lab8. Open image SA_030805_b6.tif. Band 1 is the band 6 (low gain)
   of land sat image, and band 2 is band 9 (high gain). Display band 2 using
   gray scale.

2. Introduction

       As you learned, landsat ETM+ image has 9 bands, band 1-3 is visible
bands, 4-5 and 7 is near and short wave infrared band, band 8 is panchromatic
band, band 6 and band 9 is thermal band. Band 6 is low gain thermal band and
band 9 is high gain image. *.H2 is the header file of thermal bands. These two
thermal bands are what we need to derive the temperature of land surface. You
can check the difference of these two images by linking them or performing the
statistics. The DN is actually different. You are required to compare the
difference of brightness/surface temperature in this lab. The image is a subset of
p027r040, on Aug 5, 2003, covering the urban area of San Antonio.


3. Calculate the temperature using IDL




                                                                                1
      Click IDL, and go to File -> New -> Editor, and copy the following IDL code
to the space, then the interface will look like Figure 1 below, and then save the
file as Th.pro to your own local lab8 folder. This code is for high gain of Band 6,
and equations (4) to (6) are used to covert the DN to Radiance, then Radiance to
brightness temperature, and finally compute the surface temperature from
brightness temperature. Detail information is in the article (LST.pdf) of P472
(Weng et al. 2004). In this code, we only use a single emissivity of 0.988. If you
want to do a completed project, you should use the method from the paper.




Pro Th

B6=READ_TIFF(‘C:\EES5053\.....\Lab8\SA_030805_b6.tif’, CHANNELS=[0,1],
geotiff=GTMODELTYPEGEOKEY)
   ;read Band6 high gain to B6, and channel 0 is the low gain, channel 1 is the high gain
B6h=temporary(B6(1,*,*))      ;assign the high gain (channel 1) of Band6 to B6h

L=temporary(0.0370588*B6h+3.2)           ;calculate radiance
TB=temporary(1282.71/(alog((666.09/L)+1)))           ;calculate brightness temperature
RT=temporary(TB/(1+(0.0007991666*TB)*alog(0.988)))
     ;supposing the same emissivity of 0.988
WRITE_TIFF,'C:\EES5053\.....\Lab8\ETM7_Th.tif', RT,
geotiff=GTMODELTYPEGEOKEY, /FLOAT
     ;write the temperature to an image called ETM7_Th.tif
end




                                                                                         2
                                  Figure 1

    This code is for high gain of Band 9. Before you run the program:

    (1) Change the input and output files’ path and name as the same as your
   input/output file name;

    (2) Compile the Th.pro, and you need to compile the code every time after
   you modify your code;

   (3) Run the Th.

   An ETM7_Th.tif file should be produced and output to your folder, and you
can open it in ENVI now.




                                                                           3
   Compute the low gain temperature use code Tl below.

Pro Tl

B6=READ_TIFF(‘C:\EES5053\......\Lab8\SA_030805_b6.tif’, CHANNELS=[1,0],
geotiff=GTMODELTYPEGEOKEY)
   ;read Band6 high gain to B6, and channel 1 is the low gain, channel 0 is the high gain
B6l=temporary(B6(1,*,*))      ;assign the low gain (channel 1) of Band6 to B6l

L=temporary(0.066823*B6l)          ;calculate radiance
TB=temporary(1282.71/(alog((666.09/L)+1)))           ;calculate brightness temperature
RT=temporary(TB/(1+(0.0007991666*TB)*alog(0.988)))
     ;supposing the same emissivity of 0.988
WRITE_TIFF,'C:\EES5053\......\Lab8\ETM7_Tl.tif', RT,
geotiff=GTMODELTYPEGEOKEY, /FLOAT
     ;write the temperature to an image called ETM7_Tl.tif
end


Questions (1): Compare the DN difference of low gain (band 1) and high gain
(band2). (10 points).

Questions (2): Compare the Temperature difference of low gain (ETM7_Tl.tif)
and high gain (ETM7_Th.tif). (10 points).

Questions (3): Analyze the distribution and variability of the Temperature
(ETM7_Th.tif, high gain) for the entire image area. (80 points).

       Use histogram, statistics, density slice, link with false color display of
different bands composition, and others to analyze the distribution and variability
of temperature for the entire area.




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