Converting Landsat ETM+ thermal band to temperature
The Landsat Enhanced Thematic Mapper Plus (ETM+) sensors acquire temperature data and
store this information as a digital number (DN) with a range between 0 and 255. It is possible to
convert these DNs to degrees Kelvin using a two-step process. The first step is to convert the
DNs to radiance values. The second step converts radiance data from step one into degrees
Kelvin.
You need to use ArcMap raster calculator to complete the calculation.
There are two band 6 files with the Landsat 7 data I downloaded. You are going to use
LE70200392003143EDC00_B6_VCID_1.TIF to calculate temperature.
Data: Download the data and unzip it.
1. Convert DN to Radiance using Spectral Radiance Scaling Method:
The LMin and LMax spectral radiance scaling factors can be used to convert DNs to radiance.
In your data folder, look for the file LE70200392003143EDC00_MTL.txt . Open the file using a
system editor (I use WordPad, right click the file, open with WordPad). In the file, look for the
values corresponding to the items in the formula above:
CVR1 is the new raster value of radiance you are going to calculate;
QCAL – the input raster LE70200392003143EDC00_B6_VCID_1.TIF;
LMIN - RADIANCE_MINIMUM_BAND_6_VCID_1;
LMAX - RADIANCE_MAXIMUM_BAND_6_VCID_1;
QCALMIN = 1
QCALMAX = 255
The file should look like this:
The ArcMap raster calculator formula will look like:
2. Convert Radiance to Kelvin:
Once the DNs for the thermal bands have been converted to radiance values, it is simply a matter
of applying the inverse of the Planck function to derive temperature values. The formula to
convert radiance to temperature is:
Where:
T is degrees Kelvin
CVR1 is cell value as radiance (from Section 1),
ε is emissivity (typically 0.95—you use this value),
K1 and K2 values for Landsat ETM are shown below:
The ArcMap raster calculator formula will look like:
Now your ArcMap table of content should have three layers: T, CVR1, and the original digital
number image LE70200392003143EDC00_B6_VCID_1.
Right click on each raster layer, then “properties”, then “Source”. Look for “statistics”. Answer
the following questions by taking the quiz TIR on e-learning. Submission deadline is 5:00 pm,
3/10.
Questions:
The temperature layer T:
What is the min temperature value (round to 2 decimal places):
What the max temperature value (round to 2 decimal places):
What the mean temperature value (round to 2 decimal places):
The radiance layer CVR1:
(2 points)
(2 points)
(2 points)
What is the min radiance value (round to 2 decimal places):
What is the max radiance value (round to 2 decimal places):
What is the mean radiance value (round to 2 decimal places):
(1 point)
(1 point)
(1 point)