The Future of Coastal Altimetry

Raney, R. K.; Phalippou, L.

doi:10.1007/978-3-642-12796-0_20

Cited by 22 publications

(14 citation statements)

References 24 publications

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“…These altimeters have the ability to work in Synthetic Aperture Radar (SAR) mode in the coastal zone. Among others, this will increase the spatial resolution in the along-track direction considerably, i.e., down to 250 m. The finer resolution implies that the radar pulses are less disturbed by land-features in the coastal zone and offer a better ability to resolve features with correlation lengths of less than 1 km [48]. Consequently, we envisage that SAR-mode altimetry will generate more data right at the coast.…”

Section: Discussionmentioning

confidence: 99%

Observed Sea-Level Changes along the Norwegian Coast

Breili

Simpson

Nilsen

2017

JMSE

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Norway's national sea level observing system consists of an extensive array of tide gauges, permanent GNSS stations, and lines of repeated levelling. Here, we make use of this observation system to calculate relative sea-level rates and rates corrected for glacial isostatic adjustment (GIA) along the Norwegian coast for three different periods, i.e., 1960 to 2010, 1984 to 2014, and 1993 to 2016. For all periods, the relative sea-level rates show considerable spatial variations that are largely due to differences in vertical land motion due to GIA. The variation is reduced by applying corrections for vertical land motion and associated gravitational effects on sea level. For 1960 to 2010 and 1984 to 2014, the coastal average GIA-corrected rates for Norway are 2.0 ± 0.6 mm/year and 2.2 ± 0.6 mm/year, respectively. This is close to the rate of global sea-level rise for the same periods. For the most recent period, 1993 to 2016, the GIA-corrected coastal average is 3.5 ± 0.6 mm/year and 3.2 ± 0.6 mm/year with and without inverse barometer (IB) corrections, respectively, which is significantly higher than for the two earlier periods. For 1993 to 2016, the coastal average IB-corrected rates show broad agreement with two independent sets of altimetry. This suggests that there is no systematic error in the vertical land motion corrections applied to the tide-gauge data. At the same time, altimetry does not capture the spatial variation identified in the tide-gauge records. This could be an effect of using altimetry observations off the coast instead of directly at each tide gauge. Finally, we note that, owing to natural variability in the climate system, our estimates are highly sensitive to the selected study period. For example, using a 30-year moving window, we find that the estimated rates may change by up to 1 mm/year when shifting the start epoch by only one year.

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Section: Discussionmentioning

confidence: 99%

Observed Sea-Level Changes along the Norwegian Coast

Breili

Simpson

Nilsen

2017

JMSE

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“…The behavior of this echo is analyzed as a function of the direction of antenna mispointing. Since the mispointing has a different behavior on beam-limited and pulse-limited altimetry [26], [27], the study separates along-and across-track mispointing angles. The second contribution of this work is the derivation of estimators for the parameters associated with the previously derived multilook echo.…”

Section: Including Antenna Mispointing In a Semi-analyticalmentioning

confidence: 99%

Including Antenna Mispointing in a Semi-Analytical Model for Delay/Doppler Altimetry

Halimi¹,

Mailhes²,

Tourneret³

et al. 2015

IEEE Trans. Geosci. Remote Sensing

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Delay/Doppler altimetry (DDA) aims at reducing the measurement noise and increasing the along-track resolution in comparison with conventional pulse-limited altimetry. In a previous paper, we have proposed a semi-analytical model for DDA, which considers some simplifications as the absence of mispointing antenna. This paper first proposes a new analytical expression for the flat surface impulse response (FSIR), considering antenna mispointing angles, a circular antenna pattern, no vertical speed effect, and uniform scattering. The 2-D delay/Doppler map is then obtained by a numerical computation of the convolution between the proposed analytical function, the probability density function of the heights of the specular scatterers, and the time/frequency point target response of the radar. The approximations used to obtain the semi-analytical model are analyzed, and the associated errors are quantified by analytical bounds for these errors. The second contribution of this paper concerns the estimation of the parameters associated with the multilook semi-analytical model. Two estimation strategies based on the least squares procedure are proposed. The proposed model and algorithms are validated on both synthetic and real waveforms. The obtained results are very promising and show the accuracy of this generalized model with respect to the previous model assuming zero antenna mispointing.

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“…We distinguish between two approaches that have been focusing on improving the altimetric technology or improving the processing of the available data. The first approach is based on reducing the measurement noise of conventional altimeters (such as Topex and Poseidon- 3) by increasing the number of observations (looks). This can be achieved by keeping the same conventional technology and improving the altimeter characteristics (as for AltiKa [1]- [3]), or by using a new delay/Doppler processing [4] that results in a different echo's shape [5]- [7].…”

Section: Introductionmentioning

confidence: 99%

“…The first approach is based on reducing the measurement noise of conventional altimeters (such as Topex and Poseidon- 3) by increasing the number of observations (looks). This can be achieved by keeping the same conventional technology and improving the altimeter characteristics (as for AltiKa [1]- [3]), or by using a new delay/Doppler processing [4] that results in a different echo's shape [5]- [7]. The second approach processes the available data by using improved models for the altimetric echoes [8]- [11] or improved estimation algorithms [12]- [14].…”

Section: Introductionmentioning

confidence: 99%

Bayesian Estimation of Smooth Altimetric Parameters: Application to Conventional and Delay/Doppler Altimetry

Halimi

Mailhes

Tourneret

et al. 2016

IEEE Trans. Geosci. Remote Sensing

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This paper proposes a new Bayesian strategy for the smooth estimation of altimetric parameters.The altimetric signal is assumed to be corrupted by a thermal and speckle noise distributed according to an independent and non identically Gaussian distribution. We introduce a prior enforcing a smooth temporal evolution of the altimetric parameters which improves their physical interpretation. The posterior distribution of the resulting model is optimized using a gradient descent algorithm which allows us to compute the maximum a posteriori estimator of the unknown model parameters.This algorithm presents a low computational cost which is suitable for real time applications.The proposed Bayesian strategy and the corresponding estimation algorithm are validated on both synthetic and real data associated with conventional and delay/Doppler altimetry. The analysis of real Jason-2 and Cryosat-2 waveforms shows an improvement in parameter estimation when compared to the state-of-the-art estimation algorithms.

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The Future of Coastal Altimetry

Cited by 22 publications

References 24 publications

Observed Sea-Level Changes along the Norwegian Coast

Observed Sea-Level Changes along the Norwegian Coast

Including Antenna Mispointing in a Semi-Analytical Model for Delay/Doppler Altimetry

Bayesian Estimation of Smooth Altimetric Parameters: Application to Conventional and Delay/Doppler Altimetry

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