As part of the Using Satellite Data for Analysis in Starboard series, this article explains how satellite imagery of varying resolutions can be applied to different maritime domain awareness (MDA) strategies in the Starboard platform.
What is the resolution of my satellite image?
When satellite data is ingested into Starboard, the Added satellite data panel will include details on the provider, satellite constellation, and pixel size (resolution) for each acquisition in the timeline.
The spatial resolution of this image is 0.4m, as specified in the Added satellite data panel.
The spatial resolution of EO and SAR imagery in Starboard is measured in pixel size, which is indicative of the level of detail produced in the satellite image. Think of pixel size like tiles in a mosaic—smaller tiles produce a more detailed picture. Earth observation satellites can have resolutions from several hundred metres down to less than a metre.
For example, 0.4m resolution means there is approximately 40cm between pixels, whereas 10m resolution means that each pixel in an image can span approximately 10 metres.
These examples of differing resolutions are taken from our Youtube Masterclass, which compares WorldView high resolution EO (0.4m), PlanetScope medium resolution EO (3m), and Sentinel-1 low resolution SAR (10m) for the same vessels on the same day.
Which resolutions can detect vessels?
To reliably detect individual ships, resolution typically needs to be 10–30m or better, depending on the size of the vessel.
Low resolution (10–30 m) detects large vessels only,
Medium resolution (3–10 m) detects small–medium vessels
High resolution (<1 m) identifies vessel features and small boats down to a few metres in length.
At lower resolutions, the Copernicus program provides free access to images collected from Landsat (EO at 30m resolution), Sentinel-1 (SAR at 10m) or Sentinel-2 (EO at 10m) constellations. Starboard routinely ingests and integrates this data with AIS, which can be made available to your organisation on request, via support@starboard.nz.
Low resolution EO
On the other end of the spectrum, high resolution commercial satellites have submetre resolution which makes a significant difference to the interpretability of the resulting images, but often comes at a higher financial cost. At this resolution, small boats can be spotted, but the sensor must be tasked with high accuracy as it will only capture around 200 nm² per image (roughly the size of Singapore).
High resolution EO
The fundamental tradeoff between image footprint and resolution is particularly relevant to EO and SAR satellite sensors. Generally speaking, the higher the resolution, the smaller the footprint and higher the cost.