Improved Characterization of Forest Transmissivity Within the L-MEB Model Using Multisensor SAR Data

This letter proposes a novel way to assimilate synthetic aperture radar (SAR) data to L-band Microwave Emission of the Biosphere (L-MEB) model to enhance model performance over forested areas. L-and C-band satellite SAR data are used in order to characterize the forest transmissivity within the emission model, instead of the optical satellite imagery-based leaf area index (LAI) parameter. Examination of several combinations of satellite SAR data as a substitute for LAI within the L-MEB model showed that when ALOS PALSAR (L-band) and multitemporal composite Sentinel-1 (C-band) data are applied, an improved agreement was achieved between the measured and simulated brightness temperatures (TBs) over forests. The root mean squared difference between modeled and measured TBs was reduced from 6.1 to 4.7 K with single PALSAR scene-based transmissivity correction and down to 4.1 K with multitemporal Sentinel-1 composite-based transmissivity correction. Suitability of single Sentinel-1 scenes varied based on seasonal and weather conditions. Overall, this indicates the potential of an SAR-based estimation of forest volume transmissivity and opens a possible way of fruitful active-passive microwave satellite data integration.Peer reviewe

A Novel Approach to Detect Malicious User Node by Cognition in Heterogeneous Wireless Networks

Cognitive Networks are characterized by their intelligence and adaptability. Securing layered heterogeneous network architectures has always posed a major challenge to researchers. In this paper, the Observe, Orient, Decide and Act (OODA) loop is adopted to achieve cognition. Intelligence is incorporated by the use of discrete time dynamic neural networks. The use of dynamic neural networks is considered, to monitor the instantaneous changes that occur in heterogeneous network environments when compared to static neural networks. Malicious user node identification is achieved by monitoring the service request rates generated to the cognitive servers. The results and the experimental study presented in this paper prove the improved efficiency in terms of malicious node detection and malicious transaction classification when compared to the existing systems

IMSI report no. 2 : The Baltic Sea ice field campaign 17-24 March 1997 : Data report

Sisältää myös toisen artikkelin: Ari Seinä, Hannu Grönvall, Mikael Nizovsky & Jouni Vainio: IMSI report no. 3: Dissemination of test products to selected users in the Baltic Sea area : Report on activities in the winter of 199

SAR Coherence Tomography For Boreal Forest With Aid of Laser Measurements

In this paper we evaluate X- and L-band SAR coherence tomography in boreal forest with the help of detailed digital terrain and canopy height models, produced by laser scanning. Polarimetric coherence tomography (PCT) needs accurate estimates of ground phase and tree height. Supplemental accurate elevation models allow us to evaluate the performance of PCT in normal case when initial values are derived from RVoG model inversion and provides opportunity to use PCT for nonpolarimetric data. The work is based on E-SAR Lband and X-band measurements in Finland. Our results show that with accurate elevation and tree height information single polarizationX-band coherence tomography is feasible and works well. Accurate ground elevation information improves also the performance of fully polarimetric repeat pass L-band PCT. The laser DEM provides better ground phase estimate than RVoGmodel inversion in the presence of temporal decorrelation. Our results show that accurate ground phase estimation ismore critical for successful coherence tomography than other parameters

Dielectric Paper Project 5450 - Original figures

http://deepblue.lib.umich.edu/bitstream/2027.42/21132/2/rl2007.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/21132/1/rl2007.0001.001.tx

Forest Height Estimates for Boreal Forest Using L and X Band Pol-InSAR and Hutscat Scatterometer

In this paper we present a airborne polarimetric interferometric SAr measurement campaign, carried out in Finland in 2003. The main aim of the FinSAR campaign was to validate POLinSAR tree height retrieval algorithms for boreal forest and it was arranged jointly by Helsinki University of Technology (TKK) and German Aerospace Center (DLR) Microwaves and Radar Institute. During the campaign ariborne DLR's E-SAR radar (operating at L and X band) and TKK's HUTSCAT scatterometer (operating at X- and C- band) were operated over a boreal forest test site to retrieve tree height. The tree height from fully polarimetric L-band SAR data was retrieved by Random Volume over Ground inversion and it was compared with scatterometer measurements and forest stand wise inventory tree height values. Additionally we calculated tree height from X band single polarisation interferometric images by means of restricted RVoG model inversion and compared teh results with other data. Our results show that the tree heith values, estimated by means of two different radar instruments are in good agreement. We also found that single band X band data allows to calculate the mean tree height with surprinsingly good accuracy

Coherence Tomography for Boreal Forest: Camparison with HUTSCAT Scatterometer Measurements

In this paper we report on X- and L-band polarization coherence tomography in boreal forest structure mapping. We take advantage of HUTSCAT ranging scatterometer measurements and compare E-SAR derived vertical structure profiles with measured vertical scattering profiles. HUTSCAT measurements provide vertical scattering profile of the canopy and also provide supplemental forest height and ground phase estimates, allowing calculation of coherency profiles with alternative initial values. We present single baseline tomography for X-band and multibaseline tomography for L-band calculated with various initial values and compare the results with actual measurements of scattering profiles