Steps to creating synthetic images of wildland fire

Anthony VodacekCenter for Imaging Science

Rochester Institute of TechnologyApril 14, 2005

Flame Visualization– 3D Flame structure is not explicitly in the NCAR model nor is it in the fire propagation

code– Does it matter if we create realistic flame structure and smoke?

• Needed for creating realistic synthetic images from model outputs for comparison to real images of a fire scene• Needed for better visualization for the fire manager

– How do we create realistic flame structure?• Temperature data• Real spectral data and blackbody spectral model• Attenuation coefficient through flame• 3D modeling of an emissive transparent object (a gas)

Albany NY pinebushthermocouple at surfaceof mineral soil

Temperature data

Real Flame spectra and blackbody model

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Infrared Systems spectrometercontinuously variable filter

ASD spectrometer

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Flame thickness and radianceSeries of measurements on experimental fires at the Fire Science Lab

Flame thickness and radiance

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Flame thickness, feetFlame thickness, feet

• Optically thin result, relative radiance was linear with temperature• Attenuation coefficient is very small

Digital Imaging and Remote Sensing Image Generation Model (DIRSIG)• A first principles ray tracing code that is spectral (visible to thermal)• Facetized solid reflective surfaces• Transmissive objects (tree leaves, gas plumes)• Thermal history• MODTRAN atmospheric model• Sensor model

Voxels in DIRSIG• A voxel is a 3D pixel• Transmission through voxels (an attenuation coefficient)• Voxel temperature (800 C)

Voxel emission -- for now

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• The voxel is an emitting source to the sensor• We can do this now, see example• New measurements at Missoula needed to determine spectral attenuation

Voxel emission – the future

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• The voxel as a secondary source• New coding in DIRSIG is required. Ready by August?

Buoyancy output from the NCAR modelIn general, the higher the buoyancy, the relatively warmer the atmosphere

Display buoyancy as grayscale

Lower threshold, larger region, looks like smoke Higher threshold, smaller region, looks like flame

Original data from Janice Coen, NCAR

grass fireDIRSIG scene •3D voxels• 1073K blackbody• ~10 m flames• RGB (lines)• Grass on ground• No reflection from the fire to the ground

DIRSIG 2.2 m WASP image, Albany, NYPrescribed burn

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