NBRT

The Normalized Burn Ratio Thermal (NBRT)

The Normalized Burn Ratio Thermal (NBRT) was developed based on the idea that burned land has low NIR reflectance (less vegetation), high SWIR reflectance (think  ash), and high brightness temperature (Holden et al. 2005). Unlike the other indices, a lower NBRT means more burning. Implement the NBRT with an expression:

nbrt.png

An example of Portugal here or use the code below:

<i><span style="font-weight:400;">// User specified parameters</span></i>

<i><span style="font-weight:400;">// setup Visualization</span></i>
<b>var</b><span style="font-weight:400;"> viz = {min:</span><span style="font-weight:400;">1.0</span><span style="font-weight:400;">, max:</span><span style="font-weight:400;">0.9</span><span style="font-weight:400;">, palette:[</span><span style="font-weight:400;">'green'</span><span style="font-weight:400;">, </span><span style="font-weight:400;">'blue'</span><span style="font-weight:400;">, </span><span style="font-weight:400;">'yellow'</span><span style="font-weight:400;">, </span><span style="font-weight:400;">'red'</span><span style="font-weight:400;">]};</span>

<i><span style="font-weight:400;">// Data</span></i>

<i><span style="font-weight:400;">// get landsat 8 image</span></i>
<b>var</b><span style="font-weight:400;"> image = ee.Image(</span><span style="font-weight:400;">"LANDSAT/LC08/C01/T1_RT_TOA/LC08_204032_20170802"</span><span style="font-weight:400;">);</span>

<i><span style="font-weight:400;">// Functions</span></i>

<i><span style="font-weight:400;">// calculate nbrt</span></i>
<b>var</b><span style="font-weight:400;"> nbrt = image.expression(</span>
<span style="font-weight:400;">  </span><span style="font-weight:400;">'(NIR - 0.0001 * SWIR * Temp) / (NIR + 0.0001 * SWIR * Temp)'</span><span style="font-weight:400;">, {</span>
<span style="font-weight:400;">    </span><span style="font-weight:400;">'NIR'</span><span style="font-weight:400;">: image.select(</span><span style="font-weight:400;">'B5'</span><span style="font-weight:400;">),</span>
<span style="font-weight:400;">    </span><span style="font-weight:400;">'SWIR'</span><span style="font-weight:400;">: image.select(</span><span style="font-weight:400;">'B7'</span><span style="font-weight:400;">),</span>
<span style="font-weight:400;">    </span><span style="font-weight:400;">'Temp'</span><span style="font-weight:400;">: image.select(</span><span style="font-weight:400;">'B11'</span><span style="font-weight:400;">)</span>
<span style="font-weight:400;">});</span>

<i><span style="font-weight:400;">// Add to map</span></i>
<span style="font-weight:400;">Map</span><span style="font-weight:400;">.addLayer(nbrt,viz,</span><span style="font-weight:400;">"Wildfire portugal"</span><span style="font-weight:400;">);</span>
<span style="font-weight:400;">Map</span><span style="font-weight:400;">.centerObject(nbrt,</span><span style="font-weight:400;">7</span><span style="font-weight:400;">)</span>

 

2 comments

  1. NBRT doesn’t need the prefire image? NBRT is the addition to (Normalized Burn Ratio (NBR) and in NBR, we find the difference between the prefire and postfire image to get the difference. (DNBR)

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  2. NBRT is the addition to Normalized Burn Ratio (NBR) which requires both prefire and postfire images to find the differenced NBR (DNBR). So NBRT doesn’t need the prefire image?

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