• Estimation of Ambiguity Functions With Limited Spread 

      Hindberg, Heidi; Olhede, Sofia C. (Research report; Forskningsrapport, 2008-04-07)
      This paper proposes a new estimation procedure for the ambiguity function of a non-stationary time series. The stochastic properties of the empirical ambiguity function calculated from a single sample in time are derived. Different thresholding procedures are introduced for the estimation of the ambiguity function. Such estimation methods are suitable if the ambiguity function is only non-negligible ...
    • The harmonizable representation of complex-valued nonstationary random processes 

      Hindberg, Heidi (Master thesis; Mastergradsoppgave, 2005-06-14)
      In this thesis we study the second-order statistical moment functions that characterizes complex-valued harmonizable processes. A real-valued harmonizable process has four Hermitian second-order functions. These functions are equivalent representations of the second-order statistical quantities of the process. For a complex-valued harmonizable process, however, we need the complementary functions ...
    • Recent acceleration of a rock glacier complex, Ádjet, Norway, documented by 62 years of remote sensing observations 

      Eriksen, Harald Øverli; Rouyet, Line; Lauknes, Tom Rune; Berthling, Ivar; Hindberg, Heidi; Larsen, Yngvar; Corner, Geoffrey D. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-23)
      Recent acceleration of rock glaciers is well recognized in the European Alps, but similar behavior is hardly documented elsewhere. Also, the controlling factors are not fully understood. Here we provide evidence for acceleration of a rock glacier complex in northern Norway, from 62 years of remote sensing data. Average annual horizontal velocity measured by aerial feature tracking increased from ...
    • Satellite-Based National Intertidal-Zone Mapping of Continental Norway with Sentinel-1&2 

      Haarpaintner, Jörg; Davids, Corine; Hindberg, Heidi; Arntzen, Ingar M; Borch, Njål Trygve (Research report; Forskningsrapport, 2021-05-21)
      The report describes updated methods that were originally developed in Haarpaintner & Davids (2020) to map the intertidal zone, in terms of atmospheric exposure, type and areal extent, based on radar and optical high resolution (10m) satellite imagery from Sentinel-1A/B (C-band synthetic aperture radar, C-SAR) and Sentinel-2A/B (multi-spectral instruments) of the European Copernicus Program. It ...
    • Time-frequency characterization of harmonizable random processes 

      Hindberg, Heidi (Doctoral thesis; Doktorgradsavhandling, 2009)
      In this thesis we study how to characterize nonstationary harmonizable random processes simultaneously in time and frequency. Unlike stationary random processes, harmonizable processes can have a frequency content that changes with time. Rather than working directly with the process itself, we analyze the second-order moment functions of the process and characterize the process from these moments. ...