Estimation of Forest Biomass and Faraday Rotation Using Polarimetric L-/P-band SAR

• At present the greatest source of uncertainty in the global carbon cycle is in the terrestrialecosystems. In order to reduce these uncertainties it is necessary to provide consistent andaccurate global estimates of the biomass contained in the forests of the world. One of themost promising methods for obtaining such estimates is through polarimetric SARbackscatter measurements at L-and P-band frequencies. This thesis aims to investigate thepossibility of retrieving forest biomass from L- or P-band SAR backscatter data. It alsoconcerns SAR image calibration. Well calibrated systems are necessary to ensure that errorsin estimates of physical properties, e.g. forest biomass, are not enlarged by noise or imagedistortions. Both system distortions, such as leakage between polarization channels, anddistortions caused by the ionosphere are studied.A calibration analysis was made on data from the L-band PALSAR system onboard theJapanese ALOS satellite. The data was shown to be of good quality, especially in terms ofradiometric stability and leakage between polarization channels. Following this an analysis ofFaraday rotation, i.e. image distortions caused by the ionosphere, was made for the PALSARimages. It was shown that Faraday rotation can be measured and corrected in PALSARimage, at least if the Faraday rotation is small.Forest biomass retrieval algorithms for P- and L-band SAR backscatter were developed andevaluated using data from the BioSAR-I campaign conducted in southern Sweden in 2007. Itwas found that HV- and HH-polarized backscatter was strongly related to biomass for both LandP-band. However, the L-band backscatter was found to have decreased sensitivity tobiomass for forest stands with biomass larger than about 200 tons/ha, resulting in anincreased error in the biomass estimates. For P-band this problem was not seen, and it wasfound that the biomass on stand level could be estimated using HV- and /or HH-polarized Pbandbackscatter with an error of 20-25% of the mean biomass for stands with biomassranging from 10 to 290 tons/ha.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Rymd- och flygteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Aerospace Engineering (hsv//eng)

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Jordbruksvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Agricultural Science (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Naturresursteknik -- Annan naturresursteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Environmental Engineering -- Other Environmental Engineering (hsv//eng)

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Skogsvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Forest Science (hsv//eng)

Keyword

linear regression

Remote sensing

forest biomass retrieval

P-band

synthetic aperture radar (SAR)

calibration

L-band

Publication and Content Type

lic (subject category)

vet (subject category)