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)

2

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

Presentatör

Presentationsanteckningar

BIOMASS will produce a series of global maps of forest biomass, forest height and forest disturbance at a precision, accuracy and resolution that will revolutionise our knowledge of the biosphere, its dynamics, and its interactions with the atmosphere.

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

Presentatör


Biomass is a key part of the global carbon cycle, a cycle for which we have overwhelming evidence of human induced perturbations, as this figure shows. Fossil fuel burning and land use change are adding billions of tons of CO2 to the atmosphere each year. This increase in greenhouse gases is leading directly to climate warming, potentially endangering human development and even our civilisation. However, we also know that the biosphere is acting as a sink, absorbing CO2 from the atmosphere and slowing warming. The location and even the magnitude of this sink are, however, unknown. To understand, mitigate and adapt to climate change we must resolve these uncertainties in the global carbon cycle, and that means mapping biomass. The BIOMASS mission will help resolve the fate of anthropogenic CO2 emissions, which are currently so poorly known.

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?

Presentatör


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

Presentatör


Tropics and Asia have limited inventory systems, incomplete data, high biomass and ongoing LUC. Climate change, including warming and drought may have impacts in tropical and boreal zones. Reforestation is occurring in China at high rates. Global Forest Observations Initiative and REDD areas are located in the tropics

PolSAR (SAR Polarimetry)

x

y

z

o

PolInSAR (Polarimetric SAR Interferometry)

x

y

z

o

TomoSAR (SAR Tomography)

x

y

z

o

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

he

re C

orr

ec

tio

n

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

16

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

mapping of above-ground forest biomass with satellite synthetic

Documents