14 Feb 2023
 | 14 Feb 2023
Status: this preprint is currently under review for the journal TC.

A Comparison of CFAR Object Detection Algorithms for Iceberg Identification in L- and C-band SAR Imagery of the Labrador Sea

Laust Færch, Wolfgang Dierking, Nick Hughes, and Anthony P. Doulgeris

Abstract. In this study, we pursue two objectives: first, we compare six different “Constant-False-Alarm-Rate" (CFAR) algorithms for iceberg detection in SAR images, and second, we investigate the effect of radar frequency by comparing the detection performance at C- and L-band. The SAR images were acquired over the Labrador Sea under melting conditions. In an overlapping optical Sentinel-2 image, 492 icebergs were identified in the area. They were used for an assessment of the algorithms’ capabilities to accurately detect them in the SAR images and for the determination of the number of false alarms and missed detections. By testing the detectors at varying probability of false alarm (PFA) levels, the optimum PFA for each detector was found. Additionally, we considered the effect of iceberg sizes in relation to image resolution. The results showed that the overall highest accuracy was achieved by applying a Log-normal CFAR detector to the L-band image (F-score of 70.4 %), however, only for a narrow range of PFA values. Three of the tested detectors provided high F-scores above 60 % over a wider range of PFA values both at L- and C-band. Low F-scores were mainly caused by missed detections of small (< 60 m) and medium-sized (60–120 m) icebergs, with approximately 20–40 % of the medium icebergs and 85–90 % of small icebergs being missed by all detectors. The iDPolRad detector which is sensitive to volume scattering is less suitable under melting conditions.

Laust Færch et al.

Status: open (extended)

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  • RC1: 'Comment on tc-2023-17', Anonymous Referee #1, 15 Mar 2023 reply

Laust Færch et al.

Laust Færch et al.


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Short summary
Icebergs in open water are a risk to maritime traffic. In this study, we have compared 6 different constant false alarm rate (CFAR) detectors on overlapping C- and L-band Synthetic Aperture Radar (SAR) images for the detection of icebergs in open water, with a Sentinel-2 image used for validation. The results revealed that L-band gives a slight advantage over C-band, depending on which detector is used. Additionally, the accuracy of all detectors decreased rapidly as the iceberg size decreased.