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S. Lehner et al.
Fig. 15.12 TerraSAR-X Stripmap sub-image (HH-Pol, 3 m resolution) acquired on 16 December
2008 over the southern Africa near Cape Town with ships detected by the DLR ship detection
algorithm (red superimposed AIS (source: HIS Fairplay) data with green rectangles, and Satellite
AIS reports (yellow rectangles, source: Luxspace)
by SAR are superimposed and marked by red rectangles. Collocated ships with
terrestrial AIS messages are marked by green rectangles.
Bright point detection is sometimes not sufficient and when used itself not able to
avoid detections related to oceanographic features, e.g. breaking waves or meteorological events like rain cells (Brusch et al. 2008). Further errors can arise from SAR
image artefacts, such as side lobes, azimuth ambiguities from land or strong point
targets over the open sea. The distance of azimuth ambiguities Δx to point targets is
calculated by:
Δx = Δt ambi
∗ f 0
(15.3)
where f 0 is the Zero Doppler Velocity and
Δt ambi =
PRF
FM
(15.4)
S. Lehner et al.
Fig. 15.12 TerraSAR-X Stripmap sub-image (HH-Pol, 3 m resolution) acquired on 16 December
2008 over the southern Africa near Cape Town with ships detected by the DLR ship detection
algorithm (red superimposed AIS (source: HIS Fairplay) data with green rectangles, and Satellite
AIS reports (yellow rectangles, source: Luxspace)
by SAR are superimposed and marked by red rectangles. Collocated ships with
terrestrial AIS messages are marked by green rectangles.
Bright point detection is sometimes not sufficient and when used itself not able to
avoid detections related to oceanographic features, e.g. breaking waves or meteorological events like rain cells (Brusch et al. 2008). Further errors can arise from SAR
image artefacts, such as side lobes, azimuth ambiguities from land or strong point
targets over the open sea. The distance of azimuth ambiguities Δx to point targets is
calculated by:
Δx = Δt ambi
∗ f 0
(15.3)
where f 0 is the Zero Doppler Velocity and
Δt ambi =
PRF
FM
(15.4)