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LWIR_MWIR

Infrared light and colors used for mapping fires

Thermal infrared (IR) is light emitted by objects. Fire puts out a lot of this light that humans can not see, but they feel as heat. IR cameras can focus this heat into a recordable image. Reflective light outdoors uses sunlight that reflects off the object. Color is the only light human eyes can see.

14-bit Long Wave IR (LWIR) is the best for fire mapping and visual reference. It is a very low cost, low power, small to tiny, plenty of pixel depth and radiometric resolution (temperature readout).  Medium Wave IR (MWIR) is good too, but many times the size and cost for maybe no gain.  MWIR has more zoom lens options available, but for fire mapping, these are not needed. 

Long Wave Infrared (LWIR) 7-14 micron. The best for firefighting. It shows mountains, fire and vegetation through thick smoke and dark. 14-bit has xxxxx shades of grey which equate to temperatures ranging from 0F to 2000 f. Older microbolometers have more noise but new ones much less.  Above LWIR is Microwaves used for ovens, radar and radio communications. Sees through smoke and haze best. Will see through thin clouds but not thick ones.

Middle Wave Infrared (MWIR) 3-7 micron. Known for being crisper than LWIR in 8-bit images, but 14-bit is about the same. Much more expensive, larger and requires a sensor cooler (refrigeration). Data is usually less noisy but new LWIR is matching it.  Sees through smoke and haze best. Will see through thin clouds but not thick ones.

14-bit thermal (MWIR or LWIR) allows the same photo or video to show detail in both cold ground vegetation adjacent to detail of high heat fire. In 8-bit will show one or the other. 14-bit can be re-processed (like PhotoShop) to show different details not visible to the human eye in real-time, like fire bloom. Bloom is the bright haze surrounding intense fire heat, but this can be eliminated with image processing of 14-bit imagery.

Short Wave Infrared (SWIR) 1.1-3 micron/1000-3000 Nanometers. Can be slightly useful but limited and mostly redundant. Used occasionally for visualizing fire and ground and vegetation along with fire during the day. At night the reflective sunlight is absent, and thermal is not as good as LWIR and MWIR. Not best for mapping.  Very good for oil spill mapping.

Near-Infrared (NIR).  .8-1.1 Micron/800-100 Nanometers. Not relevant to firefighting. Used for plant analysis during the day. Does not work at night or through smoke, but does see through haze. Can be helpful sometimes when mapping the black during the day. Some people can see the lower range with their eyes, and modern cameras all see NIR, and a cut filter is used to eliminate

Color, Highest resolution and least expensive of all the cameras. Red-Green-Blue (RGB), Yellow Red Blue primary colors same as a rainbow, Cyan-Magenta-Yellow-Black (CMYK). Additive and subtractive colors. RGB vs YRB vs cyan...
red edge not relevant to fire fighting provides analytics for vegetation and agriculture

Ultraviolet (UV) Corona. Sometimes can be seen as a band in the rainbow. This light is near x rays and creates sunburns. Used for seeing electric failures and oil spills

Hybrid is a function by gimbal makers that blends lower resolution IR with high resolution color to create a more ascetically pleasing image

NDVI: Normalized Difference Vegetation Indexes are used for analyzing plant health, especially for agriculture. There are many Vegetation Indexes depending on what is being analyzed.  Not relevant to fire, but could help map black during the day

CIR: Color with Near-Infrared blended to better show vegetation. Not relevant to fire unless mapping the black during the day.

 

Cameras are typically either in gimbal, also known as a ball or FLIR ball. Or are fixed mounted as multiple same cameras for wider swath, or different camera for multispectral. Hyperspectral is many colors/IR.

 

LiDAR radiates (shines like a flashlight) microwaves (above LWIR), and reads the reflection for physical mapping.

 

Interesting point: Humans have infrared sensors like snakes. All of our skin sense thermal IR, but between our eyes and the face is the most sensitive.  Like a snake but they are more sensitive and partially focus the thermal heat.

 

 

 

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