Estimation of the Bidirectional Reflectance Distribution Function of Boreal Forest Using C-band Synthetic Aperture Radar

Albedo is known to be an important factor in climate research, and albedo is influenced by the bidirectional reflectance distribution function (BRDF). This thesis seeks to improve the accuracy of albedos calculated for boreal forests by studying methods with which BRDF could be estimated using C-ban...

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Bibliographic Details
Main Author: Riihelä, Aku
Other Authors: Manninen, Terhikki, Teknillinen korkeakoulu, Helsinki University of Technology, Sähkö- ja tietoliikennetekniikan osasto, Hallikainen, Martti, Aalto-yliopisto, Aalto University
Format: Master Thesis
Language:English
Published: 2006
Subjects:
remote sensing
boreal forest
satellite radar
SAR
BRDF
kaukokartoitus
boreaalimetsä
satelliittitutka
albedo
Sodankylä
Asar
Tähtelä
Northern Finland
Online Access:https://aaltodoc.aalto.fi/handle/123456789/94320
Description
Summary:Albedo is known to be an important factor in climate research, and albedo is influenced by the bidirectional reflectance distribution function (BRDF). This thesis seeks to improve the accuracy of albedos calculated for boreal forests by studying methods with which BRDF could be estimated using C-band synthetic aperture radars. BRDF is usually calculated from optical data, which is vulnerable to cloud contamination. This estimation method could remove cloud contamination effects and improve albedo accuracy. The study involves a three-way analysis, comparing ASAR data to BRDFs calculated from optical satellite data from SPOT-4 and ground truth LAI data. The study area is at Tähtelä, near the town of Sodankylä in Northern Finland. The study shows a relation between ASAR data and the BRDF model results. SPOT-4 derived BRDF has a better correlation to ASAR data. Based on the analysis, estimation formulae are developed for calculating the BRDF of boreal forest from ASAR data. The estimation method is then applied to full scale satellite images of the Sodankylä area and surroundings. The results are inconclusive due to incomplete data concerning the natural conditions of the large scale area. However, the results are promising and this study is likely one of the first of this type of BRDF research. Maanpinnan kirkkaus eli albedo on merkittävä tekijä ilmaston ja sen muutoksen tutkimuksessa. Eräs siihen vaikuttavista tekijöistä on pinnan heijastuksen eri valaisuja katselukulmista määräävä BRDF-funktio. Se määritetään tavallisesti optisella kaukokartoituksella, joka kuitenkin on herkkä pilvien aiheuttamille virheille. Tämä diplomityö tutkii mahdollisuutta estimoida optisesti määritettyä BRDF:ä boreaalisissa metsissä käyttämällä C-kaistan SAR-satelliittitutkaa. C-kaistan satelliittitutka ei reagoi pilviin, joten estimoinnilla voitaisiin saavuttaa tarkempia tuloksia albedon laskennassa pilvien aiheuttamien virheiden vähentyessä. Diplomityössä vertaillaan satelliittitutkan mittaustuloksia sekä SPOT-satelliitin optisesta ...

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