Maritime Monitoring

Boat Detection


Sentinel-1 provides global, regular and repeated coverage of coastal and open sea waters. With its Synthetic Aperture Radar (SAR), Sentinel-1 has the advantage of operating under cloud cover or a lack of illumination and can acquire data over a site during day or night time under all weather conditions. One of the many applications of Sentinel-1 SAR data is for Maritime Monitoring, making it suitable for vessel detection.


By monitoring ship behavior, it is possible to alert of potential illegal activities, like border crossings, infringements of maritime traffic separation schemes, and illegal fishing. Maritime surveillance is also useful to assess the use and management of the maritime space.


Sentinel-1 routinely collects large amounts of images which are made freely available. The vast amounts of data produced by the constellation of satellites are a great opportunity to develop systems for Maritime Monitoring. To become fully operational, these processing systems must be entirely automatic with a controlled level of reliability and robustness.



Synthetic Aperture Radar (SAR) Wave aquisition mode 20km by 20km at 5m spatial resolution 6 day revisit at equator

The system developed by Quasar provides a fully automatic ship detection algorithm for Sentinel-1 SAR images, providing a long-term, wide-area monitoring of vessel traffic along with vessel location and size estimators and classification. Automatic vessel detection, without human intervention, requires reliable results in order to remove false alarms which are not due to vessels.

The behavior of the vessel detection pipeline developed by Quasar, in terms of success rate as a function of boat size, is summarized in the following table:

Vessel Detection Processing Pipeline Summary
Vessel size > 10mVessel size > 20mVessel size > 30m

Precision: 0.55

Recall: 0.5625

Accuracy: 0.68

FSscore: 0.56

Precision: 0.61

Recall: 0.8055

Accuracy: 0.74

FSscore: 0.69

Precision: 0.75

Recall: 0.9167

Accuracy: 0.86

FSscore: 0.83

(1) The Precision tells us to what percentage one is sure that what is being detected is a vessel or not.

(2) The recall tells us what percentage of all ships are being detected in a given scene.

(3) Accuracy and FScore are two ways of combining Precision and Reall. Either one of these two values can be used as a value to estimate the success rate.


As an example, from the table above, for boats larger than 30 meters in length, the success rate is more than 80%, a fairly good value according to other studies.

It is important to notice that these numbers depend on many factors. Amongst them, it depends largely on the analysis window size chosen, the type of pre-processing, the probability of false alarms, the type of image, whether the area is prone to have a lot of noise, such as areas near permanent radars, the minimum size of vessels of interest to be detected, etc…

These factors should be taken into consideration since the detection capabilities of the vessel processing pipeline depends largely on the problem at hand. For example, weight can be given to detecting the maximum number of vessels in a given scene versus how reliable each single detection is. Or the opposite, fewer vessel detections in favor of a higher reliability for single detections.

Products | Applications | Services

Maritime Monitoring Products
  • Sentinel-1 SAR Processed Image
  • Vessel Detection Shapefile
  • Vessel location and size estimators
  • Oil Spill Detection Shapefile
  • Characterization of Oil Spills
Maritime Monitoring Applications

The Maritime Monitoring Products can be used for different applications. Some examples are:

  • Vessel and vessel traffic spatial density and distribution
  • Derivation of most likely vessel routes
  • Identification of static and mobile maritime objects
  • Hotspot identification and their temporal and spatial evolution
  • Autocorrelation analysis to characterize the behavior of different spatial zones
  • Temporal analysis for the extraction of trends on different time scales
  • Cross-correlation with AIS or other external sources of data
  • Cross-correlation with location of Marine Ecosystems
  • Follow the route of single large vessels over time (cruises, tankers, …)
    (*) Non time continuous coverage. Dependent on revisit time.
Maritime Monitoring Services
  • Dedicated tailor-made solutions for Sentinel-1 SAR applications
  • Consulting services about Sentinel-1 data, products and applications
  • Support the integration of Sentinel-1 data into your solution
  • Support the integration of auxiliary non-EO data into your EO solution
  • Participation in R&D projects at national and European levels with experience leading projects and working within large collaborations

Maritime Monitoring | Application Examples

Boat and Traffic Density

S1 boat detections give location and estimated boat size. Using a tessellated field (World reference tessellated (UBER H3)) density maps can be derived at any desired scale. Multi temporal analysis allows to derive most likely traffic routes together with a classification of objects as moving or static.

SAR/AIS Correlation to Monitor Ilegal Activity

S1 and AIS data comparison can provide vital information. S1 and AIS hotspot comparison and their spatial evolution with time can help identify illegal activities and to manage and monitor marine areas.

Marine Ecosystems Monitoring

S1 detections can be used to assess boat pressure over marine ecosystems. Temporal analysis of these pressure points can be used to monitor seasonal boat activity and help in putting measures in place to protect marine ecosystems. Autocorrelation studies can help to characterize the behaviour of different spatial zones.