The mean echo and echo cross product from a beamforming interferometric altimeter and their application to elevation measurement

Wingham, D. J.; Phalippou, L.; Mavrocordatos, C.; Wallis, David

doi:10.1109/tgrs.2004.834352

Cited by 93 publications

(88 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In SARIn, SIRAL uses two receiver antennae to perform interferometry, allowing the location of the point of closest approach (POCA) to be precisely determined in the acrosstrack plane (Wingham et al, 2004). Bursts of 64 pulses are emitted at a high pulse repetition frequency, and Doppler processing is then used to reduce the along-track footprint to approximately 300 m (Wingham et al, 2006).…”

Section: Cryosat-2 Elevation Measurementsmentioning

confidence: 99%

A new digital elevation model of Antarctica derived from CryoSat-2 altimetry

et al. 2018

View full text Add to dashboard Cite

Abstract. We present a new digital elevation model (DEM) of the Antarctic ice sheet and ice shelves based on 2.5 × 10 8 observations recorded by the CryoSat-2 satellite radar altimeter between July 2010 and July 2016. The DEM is formed from spatio-temporal fits to elevation measurements accumulated within 1, 2, and 5 km grid cells, and is posted at the modal resolution of 1 km. Altogether, 94 % of the grounded ice sheet and 98 % of the floating ice shelves are observed, and the remaining grid cells north of 88 • S are interpolated using ordinary kriging. The median and root mean square difference between the DEM and 2.3 × 10 7 airborne laser altimeter measurements acquired during NASA Operation IceBridge campaigns are −0.30 and 13.50 m, respectively. The DEM uncertainty rises in regions of high slope, especially where elevation measurements were acquired in low-resolution mode; taking this into account, we estimate the average accuracy to be 9.5 m -a value that is comparable to or better than that of other models derived from satellite radar and laser altimetry.

show abstract

Section: Cryosat-2 Elevation Measurementsmentioning

confidence: 99%

A new digital elevation model of Antarctica derived from CryoSat-2 altimetry

et al. 2018

View full text Add to dashboard Cite

show abstract

“…The level 1B data products are the result of a beam formation process which sums phaseweighted and slant-range-corrected echoes taken from different look angles (see Wingham et al, 2006, for details). The received radar echo, (τ ), from a uniformly backscattering planar surface can be expressed as (e.g., Brown, 1977;Raney, 1998;Wingham et al, 2004) the convolution of the compressed transmit pulse after signal processing, P t (τ ), the surface height probability density function, p (τ ), and the "rough surface" impulse response (a factor of the surface geometry and antenna pattern), I (τ ),…”

Section: Physical Model For Cryosat-2 Echoesmentioning

confidence: 99%

An improved CryoSat-2 sea ice freeboard retrieval algorithm through the use of waveform fitting

2014

View full text Add to dashboard Cite

Abstract.We develop a physical model capable of simulating the mean echo power of CryoSat-2 SAR-and SARInmode waveforms over sea-ice-covered regions. The model simulations are used to show the importance of variations in the radar backscatter coefficient with incidence angle and surface roughness for the retrieval of surface elevation of both sea ice floes and leads. The physical model is used to fit CryoSat-2 waveforms to enable retrieval of surface elevation through the use of lookup tables and a bounded trust region Newton least-squares fitting approach. The use of a model to fit returns from sea ice regions offers advantages over currently used threshold retracking methods, which are here shown to be sensitive to the combined effect of bandwidth-limited range resolution and surface roughness variations. Laxon et al. (2013) have compared ice thickness results from CryoSat-2 and IceBridge, and found good agreement; however consistent assumptions about the snow depth and density of sea ice were not used in the comparisons. To address this issue, we directly compare ice freeboard and thickness retrievals from the waveform-fitting and threshold tracker methods of CryoSat-2 to Operation IceBridge data using a consistent set of parameterizations. The purpose of the comparison is to highlight the physical basis between differences in the retracking methods. For three IceBridge campaign periods from March 2011 to March 2013, mean differences (CryoSat-2 -IceBridge) of 0.144 and 1.351 m are found between the freeboard and thickness retrievals, respectively, using a 50 % sea ice floe threshold retracker, while mean differences of 0.019 and 0.182 m are found when using the waveform-fitting method. This suggests the waveformfitting technique is capable of better reconciling the sea ice thickness data record from laser and radar altimetry data sets through the usage of consistent physical assumptions.

show abstract

“…A comprehensive model of the power and phase of the returns has been developed by Wingham et al (2004Wingham et al ( , 2006 and used to predict waveform response, particularly for the region close to the POCA. This model was also used in CS SARIn mode calibration .…”

Section: Interferometry With Multiple Footprintsmentioning

confidence: 99%

Interferometric swath processing of Cryosat data for glacial ice topography

et al. 2013

View full text Add to dashboard Cite

Abstract. We have derived digital elevation models (DEMs) over the western part of the Devon Ice Cap in Nunavut, Canada, using "swath processing" of interferometric data collected by Cryosat between February 2011 and January 2012. With the standard ESA (European Space Agency) SARIn (synthetic aperture radar interferometry) level 2 (L2) data product, the interferometric mode is used to map the cross-track position and elevation of the "point-of-closestapproach" (POCA) in sloping glacial terrain. However, in this work we explore the extent to which the phase of the returns in the intermediate L1b product can also be used to map the heights of time-delayed footprints beyond the POCA. We show that there is a range of average cross-track slopes (∼ 0.5 to ∼ 2 • ) for which the returns will be dominated by those beneath the satellite in the main beam of the antenna so that the resulting interferometric phase allows mapping of heights in the delayed range window beyond the POCA. In this way a swath of elevation data is mapped, allowing the creation of DEMs from a sequence of L1b SARIn Cryosat data takes. Comparison of the Devon results with airborne scanning laser data showed a mean difference of order 1 m with a standard deviation of about 1 m. The limitations of swath processing, which generates almost 2 orders of magnitude more data than traditional radar altimetry, are explored through simulation, and the strengths and weaknesses of the technique are discussed.

show abstract

The mean echo and echo cross product from a beamforming interferometric altimeter and their application to elevation measurement

Cited by 93 publications

References 18 publications

A new digital elevation model of Antarctica derived from CryoSat-2 altimetry

A new digital elevation model of Antarctica derived from CryoSat-2 altimetry

An improved CryoSat-2 sea ice freeboard retrieval algorithm through the use of waveform fitting

Interferometric swath processing of Cryosat data for glacial ice topography

Contact Info

Product

Resources

About