Maritime Domain Awareness

See What Is Happening at Sea — Even When Ships Go Dark

Pick a port or chokepoint, watch it as a site, and every new Sentinel-1 radar pass is counted for vessel-like targets — whether or not they broadcast AIS. A count that breaks from the place's own history is flagged, maritime events linked to it arrive on the same watch, and you can see when the next SAR pass comes.

Open the Watchlist See maritime events

Quick answer — what Off-Nadir Delta is

Maritime domain awareness is the understanding of any activity at sea that could affect security, safety, the economy, or the environment. AIS is self-reported and can be switched off, so satellite radar fills the gap: Sentinel-1 SAR shows vessel-like targets day or night and through cloud, regardless of AIS. Off-Nadir Delta watches a port or chokepoint as a site, counts vessels on every new pass with CFAR detection, flags counts that break from the place's own history (modified z-score above 3.5), and links maritime events to the facility. It detects radar returns, not identities — pair it with AIS to name the ships.

What SAR fills in — and what it does not

What a SAR count gives you

A hull returns a strong radar signal against calm water, so a Sentinel-1 pass shows vessel-like targets whether or not their transponders are on — through cloud and at night. Counted over time at one place, it tells you when activity changes.

What it cannot tell you

Who the vessel is. A detection has no name, flag or MMSI, and it is not a ship classifier — offshore structures and sea clutter can appear too. Delta does not ingest AIS; comparing its detections with an AIS source is how you find the dark ones.

Ports & chokepoints

Pick from the registry — ports, chokepoints, named seas — or any point on the coast. No polygon to draw.

SAR, day or night

CFAR detection in Sentinel-1 through cloud and darkness; NISAR L-band on plans that include it.

Against its own history

Each count is compared with the same place's past counts, so a busy port and a quiet anchorage each have their own normal.

Maritime events

Naval, shipping and port events on the same watch, each saying whether the report named the place or is only nearby.

Next SAR pass

Predicted passes over the next 7 days for Sentinel-1, NISAR and commercial SAR — geometric access, not a guaranteed capture.

Build on it

Ship detection, monitored areas and watches are in the REST API and Python SDK. Ship detection is not an MCP tool.

Building your own pipeline? See the developer docs and the REST reference.

How It Works

Pick the port or chokepoint

Search the facility registry — ports and LNG terminals, maritime chokepoints, named seas — in many languages, or drop a point anywhere on the coast.

Watch it as a site

Add it to Delta Watchlist at facility scale (250 m to 3 km) or city scale (5 to 20 km). A port is measured from imagery by default — vessel-like targets counted in Sentinel-1 SAR. For a strait or a stretch of sea, choose vessel counts as the metric.

Count vessels on every new pass

Each new Sentinel-1 scene (or NISAR L-band, on plans that include it) is run through CFAR ship detection. The count carries its caveats: land mask unavailable, detections near the coast excluded, or only part of the area covered.

Flag the break from normal

Counts form a time series. A value is flagged when its modified z-score against the place's own median absolute deviation exceeds 3.5 — and scenes covering less than 90% of the area are kept out of that test.

Read the events, plan the next look

Maritime events linked to the facility arrive on the same watch, each stating how the link was made. Pass prediction tells you when Sentinel-1 or a commercial SAR satellite can next see the place.

Frequently Asked Questions

What is maritime domain awareness (MDA)?▼

The International Maritime Organization frames maritime domain awareness as the effective understanding of anything in the maritime domain that could affect security, safety, the economy, or the marine environment. In practice it means fusing vessel tracking (AIS), radar, satellites, patrols and reporting into one current picture of activity at sea.

What are dark vessels, and how does SAR help?▼

A dark vessel is one not broadcasting AIS — the transponder is off, spoofed, or out of receiver range. Synthetic aperture radar images day or night and through cloud, and a hull returns a strong signal against calm water, so a SAR pass can show a vessel-like target whether or not it reports itself. Comparing SAR detections with an AIS source is the usual way to find the ones that are not reporting.

Does Off-Nadir Delta ingest AIS or identify vessels?▼

No. Delta detects radar returns, not identities: a detection is a bright target on the water, with no name, flag or MMSI. Detection is not a ship classifier either — offshore structures and sea clutter can appear as targets. To find dark vessels, pair the detections with an AIS source of your choice.

Why do some counts come with caveats?▼

Because they change what the number means. If the land mask was unavailable, shoreline structures may be counted. If detections near the coast were excluded, ships alongside a quay are not in the count. If a scene covered only part of the area, the count is for that part and must not be compared with a full-coverage count — and such scenes are left out of anomaly flagging.

How does it connect vessel counts to what is being reported?▼

Delta Watchfloor classifies news and official hazard feeds into categories, including maritime (naval, shipping or port activity, vessels in distress). Events are linked to registry facilities deterministically, and each link says whether the report named the place, named it as the target, or is only nearby. At facility scale, your site watch collects those events alongside the counts.

Is it free to start?▼

You can browse and explore for free, and creating a watch is free. Measuring new imagery, running ship detection and NISAR are metered with tokens or depend on your plan. See the pricing page for current details.