Mapping of above-ground forest biomass with satellite synthetic ...
Transcript of Mapping of above-ground forest biomass with satellite synthetic ...
Lars Ulander Swedish Defence Research Agency (FOI) & Chalmers University of Technology
Mapping of above-ground forest biomass with satellite synthetic-aperture radar (SAR)
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Biomass - A candidate Earth Explorer
• ESA has six Earth Explorers launched or under development in the Living Earth Program • Launched: Cryosat-2, GOCE, SMOS • Under development: Swarm, ADM-Aeolus, Earthcare
• 7th Earth Explorer • 3 candidates completed phase A: Biomass, CoreH2O, Premiere • Biomass was recently recommended by ESAC • Final mission selection with be in May 2013. • Launch currently planned for 2019
Forest biomass Forest height Disturbances
Biomass will map global forest biomass and height
The role of biomass in the global carbon cycle
Global Carbon Project, 2012
Biomass will improve understanding and reduce uncertainties of the carbon fluxes due to land-use change and the land sink
Mapping forest biomass requires a radar sensor with long wavelength: 1. to penetrate the canopy in all forest
biomes
2. to interact with woody vegetation elements
3. so that forest height can be estimated with a single satellite
This implies a synthetic-aperture radar (SAR) at P-band, wavelength ~70 cm, the longest possible and first of its kind in space
How can biomass be measured from space?
Space Object Tracking Radar P-band constraints
Land use change
Land use change
Land use change
reforestation
fire & climate warming
drought
pests regrowth
Reducing Emissions from Deforestation & Degradation (REDD)
Global Forest Observations Initiative
Large biomass uncertainty
PolSAR (SAR Polarimetry)
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y
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PolInSAR (Polarimetric SAR Interferometry)
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TomoSAR (SAR Tomography)
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P-band SAR can deliver 3 types of information for biomass
Minimum Mean Square (MMSE)
Estimate
Biomass Estimation from
Intensity
PolSAR Covariance
Matrix
PolInSAR Covariance
Matrix
Biomass Map &
Error Map
TomoSAR results DEM
In situ data
Allometric Biomass
Estimation
Biomass Estimate 2
Biomass Estimate 1
Ion
osp
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orr
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Forest Height Estimation
Baseline biomass estimate from PolSAR & PolinSAR
La Selva, Costa Rica
Maine
Colombia
Landes Alaska
Paracou F.Guiana
Remningstorp Krycklan
Kalimantan
Major recent ESA campaigns: 1. Kalimantan 2004 (Indrex) 2. Remningstorp 2007 (BioSAR 1), 2010 (BioSAR 3) 3. Krycklan 2008 (BioSAR 2) 4. F. Guiana 2009 (TropiSAR), 2011-13 (TropiScat)
ESA campaigns non-ESA campaigns
Campaigns to develop retrieval methods and assess performance
Remningstorp forest (Sweden)
March
April May
March 2007 April 2007 May 2007
Bac
ksca
tter
Because the disturbing effects differ among polarisations, all polarisations and a DEM are used to account for environmental and topographic effects.
Soil moisture and topography affect radar-biomass relationship
Blue - from airborne lidar map, std. error = 25 ton/ha Black - from 80 m x 80 m in situ plots, std. error = few % Training on stratified subset of Krycklan data. Performance assessed on data from Remningstorp.
Remningstorp 70 MHz data: varying environmental conditions over 3 months
Sweden
Finland
Norway
Denmark
Remningstorp
N
N
N
N
HV only HV, HH & VV HV, HH, VV & DEM
RMSE: 84% RMSE: 38% RMSE: 24%
Polarisation & ground slope radically improves accuracy
Radar RMSE ~ 20 t/ha (based on 6 reference plots).
Biomass changes can be measured with improved accuracy
Lidar RMSE is comparable (slightly worse).
Change in biomass from spring 2007 to autumn 2010 at Remningstorp, Sweden
A 20 ton/ha change can be measured over a 4-year period.
-240 -160 -80 0 40 80 120 Change in biomass [ton/ha]
Height (m)
Remningstorp, Sweden
PolInSAR Lidar
r2=0.65 RMSE=4m
Height maps
Boreal height mapping using P-band PolInSAR
0
20
40
60
0
20
40
60
Normalised backscatter intensity
1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
Forest
HV
HH
Marshland River
Tomographic transects
TomoSAR: 1. Provides a 3D reconstruction of forest backscatter. 2. Allows an interpretation of scattering processes 3. Gives guidance to the PolSAR and PolInSAR retrieval algorithms.
Hei
ght (
m)
Hei
ght (
m)
HH SAR image Paracou,
French Guiana
(6 MHz bandwidth P-band data)
What about SAR tomography? It provides basic information to improve biomass retrieval algorithms
Forest biomass
Above-ground biomass (tons / hectare)
Upper canopy height (meter)
Areas of forest clearing (hectare)
• 200 m resolution • 1 map every 6 months for 4
years • global coverage of forested
areas • accuracy of 20%, or 10 t ha–1
for biomass < 50 t ha–1
• 50 m resolution • 1 map every 6 months for
4 years • global coverage of forested
areas • 90% classification
accuracy
• 200 m resolution • 1 map every 6 months for
4 years • global coverage of
forested areas • accuracy of 20-30%
Forest height Disturbances
Biomass product requirements
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Biomass - A candidate Earth Explorer
• After the User Consultation Meeting in Graz on 5-6 April 2013, the mission candidate Biomass was recommended by ESAC to become ESA’s 7th Earth Explorer
• Final decision will be taken by PBEO in May 2013
• Launch currently planned for 2019