Normalised Burn Ratio or NBR refers to the use of Landsat imagery to study the land cover change as a result of fires as well as the extent of burning.
Fire is one of nature’s most destructive forces, almost anything can be destroyed by it and, unless under perfect circumstances, is almost impossible to control. RS can be used to understand the impacts of fire on and area, particularly the impact it has on vegetation.
Healthy vegetation has a very high NIR and a low reflectance in the SWIR section of the spectrum. Once vegetation is burned (and then no longer healthy) these characteristics reverse, ie. high SWIR values and low NIR values. High NBR values generally indicates healthy vegetation while low values indicates bare earth and therefore recently burned areas (gsp.humboldt.edu, 2017).
NBR can be calculated using a formula not unlike that for calculating Normalised Difference Vegetation Index (NDVI):
Calculating NBR can be used to monitor the regrowth of vegetation following a severe fire. It is used around the world by conservationists, environmentalists, and forestry commissions.
Relative difference Normalised Burn Ratio can be used to get even more detailed results. The RdNBR allows for better a estimate of the burn severity in an area by removing the correlation of NBR and pre-fire biomass:
Fun Fact: There is a beetle (known as the Fire Beetle) that uses specialised infrared radiation sensors to detects forest fires. Once they have located the fire, they mate and lay the eggs in the scorched trees. The US Department of Defence has extensively studied the beetle’s infrared sensors in the hopes they could use it to develop heat-seeking missiles!
gsp.humboldt.edu, (2017), Normalized Burn Ratio, Available at: http://gsp.humboldt.edu/olm_2015/Courses/GSP_216_Online/lesson5-1/NBR.html, (Accessed: 19th May, 2017).
directionsmag.com, (2013), Western U.S. Disasters and Health & Air Quality: California Flames and Oregon Plains – NASA DEVELOP, Available at: http://www.directionsmag.com/entry/western-u.s.-disasters-and-health-air-quality-california-flames-and-or/324621, (Accessed: 25th May, 2017)
Thursday, May 9th, 2013