Radiative Transfer Modelling for the Characterisation of Natural Burnt Surfaces

ITT 5526:Algorithm Validation Plan (AVP)

Prof. Philip Lewis1, Dr. Mathias Disney1, Prof. Martin Wooster2, Dr. Bernard Pinty3,

Prof. David Roy4

1. UCL; 2. KCL; 3. JRC; 4. SDSU

Optical fieldwork

Rationale– Generation of 3D RT models

Key structural and radiometric measurements of canopy before/after burn

Spatial distribution of vegetation

– Validation/testing of 3D RT models Characterise before/after signal to simulate

EO signal & compare with EO data

– Site selection encompasses variations of both cover type and fire regimes

Sites: Satara

Models

Sites: Pretoriuskop

Models

Sites: Skukuza

Models

Sites: Mopani

Models

Measurement strategy

Ground-based– 2-3 transects along sites of ~200m per site,

separated by 25m– Hemiphotos, LAI2k every 10-20m, GPS’d and

marked with stakes (to survive burn), spectral measurements and scene components

Helicopter– Follow (as far as possible), same transects but

measure every 50m (ish)– Downward and oblique photography plus spectral

measurements

Measurement strategy

Models •2-3 transects of ~200m per site (avoid edge effects)•Measurements every 10-20m along transects•30-60 points per site

Optical fieldwork: structural

Tree number, location and structure

Tree location (GPS), height (clinometer), DBH (tape),

crown size (tape, clinometer)

Post burn loss of trees?

Crown size

DBH

Optical fieldwork: structural

Pre/post burn oblique aerial photography

Tree height, % tree cover

Optical fieldwork: structural

Gap fraction and LAIeff

Hemiphotos, LAIeff (LAI2000) from same locations within canopy

Optical fieldwork: radiometric (spectral)

Ground-based

•2 x ASD FS Pro spectroradiometer (350-2500nm, 1nm band width) •Following grid pattern laid out for hemiphotos etc.•1-3m above canopy (low stature) - 0.5-1m IFOV (single material)•Above smaller trees (ladder), then….

transects transects

Optical fieldwork: radiometric (spectral)

Helicopter measurements

•ASD mounted on 1.5m pole, extended from helicopter•2nd instrument measuring irradiance on the ground•Multiple measurements at multiple points in each site, from ~100m•I.e. IFOV 20-40m (scene-wide)

Optical fieldwork: radiometric (spectral)

Scene components– Leaf size, shape (photos) and using ASD contact

probe– Burned and unburned material, bark, wood etc.

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3D RT models

Models

Structure from 3D modelling software (OnyxTREE) A large range of parameters, existing models, complex/very

flexible Explicit removal of wood, leaf material (post burn)

3D RT models

Wide range of plant shapes and forms including trees, bushes and

grasses

3D RT models

Iterative parameterisation of shape, gap fraction, DBH, height, based on field measurements

– Forward modelling to compare with field measurements– Inverse to derive canopy parameters (fCOVER, LAIeff) from

observations Radiometric (leaf, trunk etc.) info. from ASD measurements

iterate

3D RT models

Spruce plantation….etc.

3D RT models

Model development requires field measurements