ERS-1 SAR Images Research Articles

Satellite imagery, a base line for glacier variation study on James Ross Island, Antarctica

Sequential visible and radar satellite imagery is used to document the fluctuations of 39 outlet glaciers on James Ross Island (JRI; 64° S, 58° W), Antarctic Peninsula. The monitoring time interval of 17.4 years extends from late 1975 until early 1993. The study is based on synergistic use of different sensors for monitoring glacier variations. The digitally enhanced Landsat TM images also allowed definition of boundaries between grounded and floating ice within Röhss Bay and detection of ice rumples, resulting in an improved measurement of the areal extent of JRI. In addition to glacier boundaries, the analyzed ERS-1 SAR images provide information on morphological properties of snow and ice. The satellite data show a general glacier retreat since 1975, resulting in clear decrease of overall glacier area on JRI. Of 39 glaciers measured, 33 glaciers retreated in the period 1975–93, 15 of which showed significant retreat in comparison to glacier size. This is in accordance with the pronounced atmospheric-warming trend recorded during the last two decades on the Antarctic Peninsula. The analysis of glacier areas on JRI thus provides a base line for detection of future changes.

Satellite imagery, a base line for glacier variation study on James Ross Island, Antarctica

Sequential visible and radar satellite imagery is used to document the fluctuations of 39 outlet glaciers on James Ross Island (JRI; 64° S, 58° W), Antarctic Peninsula. The monitoring time interval of 17.4 years extends from late 1975 until early 1993. The study is based on synergistic use of different sensors for monitoring glacier variations. The digitally enhanced Landsat TM images also allowed definition of boundaries between grounded and floating ice within Röhss Bay and detection of ice rumples, resulting in an improved measurement of the areal extent of JRI. In addition to glacier boundaries, the analyzed ERS-1 SAR images provide information on morphological properties of snow and ice. The satellite data show a general glacier retreat since 1975, resulting in clear decrease of overall glacier area on JRI. Of 39 glaciers measured, 33 glaciers retreated in the period 1975–93, 15 of which showed significant retreat in comparison to glacier size. This is in accordance with the pronounced atmospheric-warming trend recorded during the last two decades on the Antarctic Peninsula. The analysis of glacier areas on JRI thus provides a base line for detection of future changes.

Some concepts for precise estimation of deformations/rigid areas in polar pack ice based on time series of ERS-1 SAR images

Abstract This paper describes concepts for an algorithm using pairs of satellite SAR imagery to estimate precisely rigid areas and deformations in polar ice fields. The idea is first to produce a sparse sampling of the ice displacement and then identify rigid subsets of this sparse sampling. The algorithm tunes the position parameters of the images using those of these subsets best fitting the model of rigid motion (shift/rotation). Then the algorithm identifies rigid areas again and so on iteratively improving the identification of rigid areas and the relative geographical positioning in the images. The last step is to classify each pixel in the images as included in one of the given rigid areas or, perhaps, not included in one of these areas.

ERS-I SAR backscattering coefficients from bare fields with different tillage row directions

Abstract This Letter's objective is to investigate whether the periodic structuring of bare agricultural fields, brought about by tillage causes differences in backscattering coefficients (σ°) in three ERS-1 SAR images, σ° were derived for bare fields with different row directions and analysed using analysis of variance and linear regression. Results indicate significant differences in σ° for fields tilled parallel to and perpendicular to the look direction. Linear relationships between row direction and σ° are weak. The ERS-1 SAR appears sensitive to differences in the tillage row direction of bare fields but factors influencing this sensitivity must be analysed before definite conclusions are drawn.

The EODC SAR Processor

Abstract The Earth Observation Data Centre (EODC) SAR processor has now been in operational use at the U.K. Processing and Archive Facility for over a year, generating well over a thousand high quality ERS-1 SAR images in support of the ERS-1 ground segment. In this paper we discuss the characteristics of the EODC SAR processor and the images that it generates.

An ice drift series from the Fram Strait January-March 1992 based on ERS-1 SAR data

A time series of ERS-1 SAR images is used to estimate ice drift in the Fram Strait January-March 1992 (the ERS-1 mission first ice phase). The images all cover the same area. The sampling interval is three days. The paper shows examples of estimation of ice drift and divergence from this image time series. Divergence is an important quantity in order to estimate ice production and hence mixing of the ocean water masses. A reference configuration of ice points is defined for each image. These ice points are identified in the successive image giving a set of point pairs. These point pairs are input for statistical analysis. Upward looking sonars (ULS) and current meters are moored below the scene. A combination of the SAR derived dynamics and the ULS derived ice thickness series will give opportunities to estimate ice mass flux into the Greenland Sea, and to improve ice classification algorithms.

Observations of variations in ERS-1 SAR image intensity associated with forest fires in Alaska

Investigations have shown that fires in boreal forests result in characteristic responses which are recorded on ERS-1 SAR imagery. Using one of the many fire signatures observed on ERS-1 SAR imagery, the analysis of the data revealed there is >10 dB in variation in image intensity within the burned areas on the SAR images. Possible explanations for this variation include increases in soil moisture, increased surface roughness exposed to the incoming microwave radiation, and damage to the vegetation canopy by the fire. >

Eddies detected in ERS-1 SAR images and simulated in reduced gravity model

Abstract The first ERS-1 C-band SAR image of the western coast of Norway was received at Troms Satellite Station, Norway, on 21 August 1991. It depicts clearly an eddy-like structure located in the coastal water. The eddy has a cyclonic spiral structure with a diameter of about 5 km. The expressions of the dark lines outlining the spiral are probably caused by the presence of natural surface slicks resulting in a damping of the Bragg scattering waves. Eddies at this particular location with the same spatial characteristics are also detected in simulations with a nonlinear, one-layer active reduced gravity model. From the model results we conclude that the eddy is formed by horizontal current shear instability associated with variations in the larger scale coastal current. A second case of an observed and simulated eddy occurred later in the Outer Oslofjord. The simultaneous observations and simulations of these eddies clearly demonstrate the potential advantage in integrated use of weather independent SA...

Change detection on Alaska's North Slope using repeat-pass ERS-1 SAR images

Measurements of the C-band (wavelength=5 cm) radar cross section of an area in the Brooks Range foothills on the North Slope of Alaska using images from the ERS-1 satellite that show significant temporal changes occur. These changes are strongly correlated with elevation and hill-slope orientation and are greatest on some of the elevated areas and weaker in river drainages. By constructing difference images using various image pairs, and by analyzing climatological and hydrological data from the site, it is concluded that the radar backscatter changes are largely due to changes in soil and vegetation liquid water content induced by freeze/thaw events. The correlation with topography in the difference images arises from the dependence of vegetation, organic layer thickness, and volumetric water content on hill-slope position and orientation. These results demonstrate the viability of radar backscatter intensity comparisons using repeat-pass images as a means of change detection. >

Cover First ERS-1 SAR image acquired at Fucino Frisian Islands (The Netherlands)

Cover First ERS-1 SAR image acquired at Fucino Frisian Islands (The Netherlands)

Cover First ERS-1 SAR image acquired at Kiruna Salmijarvi, Spitzbergen (Norway)

Cover First ERS-1 SAR image acquired at Kiruna Salmijarvi, Spitzbergen (Norway)