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GEOM30009 IMAGING THE ENVIRONMENT
Department of Infrastructure Engineering
Assignment 2
Assessing Burn Scars Using Satellite Imagery
Objective
The aim of this assignment is to learn how to assess bush fire burn scars using Landsat images.
We will first visually compare pre-fire and post-fire Landsat images. Then, we compute two
burn index images to highlight burn scars. Finally, we create a difference normalised burn
ratio image, map fire perimeters, and calculate the total area of burn scars.
Background
Hundreds of fires burnt vast areas across New South Wales, Victoria, and Australian Capital
Territory. Satellite imagery are a useful resource that can help us assess burn scars and study
areas of vegetation regrowth. Landsat imagery is particularly suitable for assessing burn scars
because of its repeated coverage, ease of access, and spectral wavelengths. In this
assignment, we will create burn severity images using two different burn indices.
Burn area index
The Burn Area Index (BAI) highlights burnt land in the red to near-infrared (NIR) spectrum, by
emphasizing the charcoal signal. The index is computed based on the spectral distance from
each pixel to a reference spectral point resulting in an image where brighter pixels indicate
burnt areas. BAI is computed as:
Normalised burn ratio
The normalised burn ratio (NBR) highlights burnt areas in large fire zones greater than 500
acres. The formula is similar to a normalized difference vegetation index (NDVI), except that
it uses near-infrared (NIR) and shortwave-infrared (SWIR) wavelengths:
Pre-fire, healthy vegetation has a high NIR reflectance and a low SWIR reflectance. In contrast,
recently burnt areas have a relatively low NIR reflectance and a high SWIR reflectance.
Consequently, burnt areas appear dark in the NBR image whereas healthy vegetation appears
bright.
Data
Two Landsat-8 images of Kosciuszko National Park will be used for this tutorial. The first image
was acquired on 22 December 2019 and represents the pre-fire state of the park. The second
image was acquired on 23 January 2020 and represents the post-fire state of the park. Both
images can be downloaded as zip files from Canvas under “Assignment 2: Assessing Burn
Scars”. Information about the resolution and wavelength bands of Landsat-8 images can be
found on the Landsat-8 website:
We use ENVI to open and process the Landsat images. ENVI is available in the computer labs,
but you can also install it on your personal computer and connect to the license server using
the University VPN.