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Spectral band comparison for imaging through wildfire smoke

RGB, NIR, SWIR, LWIR or MWIR? We say all of the above...


We are often asked which spectral band is better for imaging active wildfires through smoke. Our answer: All of them.


Ever-changing incident and environmental factors play an enormous role in determining which spectral bands are most useful on any given flyover of a fire. Overwatch Imaging's solution to the dilemma: gather intelligence across all spectral bands simultaneously, leverage software to do the heavy lifting of data processing and dissemination, and secure the best information possible regardless of the conditions. 


OVERVIEW:

The best spectral band for imaging active wildfires through smoke depends on the conditions, type/density of smoke, and the specific imaging application. In the visible spectrum, smoke absorbs light strongly, making it difficult to see through. In general, longer wavelengths tend to penetrate smoke better than shorter wavelengths. The thermal bands (MWIR and LWIR) are particularly useful for imaging through smoke, as they capture emitted radiation that penetrates smoke and provides a clear image of fire, terrain, hot and cool spots, and the surrounding topography.


More information about Overwatch Imaging's wildfire intelligence solutions HERE.


LWIR VS MWIR:

LWIR and MWIR have their own distinct advantages when it come to imaging through smoke. In general, light penetrates smoke better in the long-wave spectrum, making LWIR innately better from a fundamental level. MWIR, on the other hand, is more sensitive to temperature variations, and thus generally better at imaging subtle thermal differences and heat sources through smoke.


SWIR vs NIR:

SWIR imaging, typically defined as the range of 900-1700 nm, has the advantage of being able to penetrate through some types of smoke and atmospheric haze that can obscure visible light and longer-wavelength infrared radiation. SWIR imaging can also be used to identify and distinguish different types of smoke, such as that produced by fires versus that produced by industrial processes.

In some circumstances, NIR imaging, typically defined as the range of 700-900 nm, can be more effective at penetrating through some types of smoke and dust than SWIR. This is because NIR light has a longer wavelength and lower energy than SWIR light, which can make it less susceptible to scattering and absorption by small particles in the air. NIR imaging can also be useful for detecting and analyzing the reflectance properties of surfaces that are obscured by smoke.



Benefits of SWIR:

Improved penetration: SWIR light can penetrate smoke and other obscurants better than visible light or near-infrared light. This can allow for better imaging of objects obscured by smoke or other materials.

Enhanced contrast: The contrast between objects and their background can be enhanced in SWIR imaging, even in the presence of smoke or other obscurants. This can make it easier to identify objects in a smoky or hazy environment.

Temperature detection: SWIR can detect temperature variations, which can be useful for detecting hotspots or fires through smoke. 


Benefits of MWIR:

High sensitivity: MWIR cameras are highly sensitive to temperature changes, making them useful for detecting small temperature variations that might indicate the presence of a fire or other heat source.

Temperature detection: MWIR can detect temperature variations, which can be useful for detecting hotspots or fires through smoke. This can help firefighters or other first responders to locate and respond to fires more quickly and effectively.

Improved penetration: MWIR light can penetrate smoke, dust, and other obscurants better than visible light, making it easier to see through smoky or hazy environments.


Benefits of LWIR:

Best wavelength for smoke penetration: LWIR light can penetrate smoke, dust, and other obscurants better than the other spectral bands.

Temperature detection: LWIR can detect temperature variations, which can be useful for detecting hotspots or fires through smoke. This can help firefighters or other first responders to locate and respond to fires more quickly and effectively.

High resolution: LWIR cameras can provide high-resolution imagery, allowing for detailed imaging of objects in a smoky or hazy environment.





Benefits of NIR:

• Enhanced vegetation monitoring: NIR light is effective for monitoring vegetation health and stress. This can help identify areas of dry or dead vegetation that are more susceptible to wildfires.

• Improved smoke penetration: NIR can penetrate through certain levels of smoke, providing clearer images than visible light. 

• Water content analysis: NIR can be used to assess the moisture content in vegetation and soil. This information is crucial for predicting fire spread and behavior, as drier areas are more likely to ignite and burn quickly




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