Maritime Domain Awareness

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

Maritime domain awareness depends on more than AIS, because vessels can switch it off. Off-Nadir Delta gives you the satellite half — verify maritime risk from space: detect vessels in Sentinel-1 SAR regardless of AIS, watch chokepoints over time, and tie maritime event signals to imagery.

See SAR Ship Detection Open the Watchfloor

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. Because AIS is self-reported and can be switched off, satellite imagery fills the gap: Sentinel-1 SAR detects vessels day or night and through cloud, regardless of AIS. Off-Nadir Delta provides that satellite layer — SAR vessel detection, chokepoint monitoring over time, and geolocated maritime event signals — with no GIS software and no code.

Why satellites fill the AIS gap

The limit of AIS alone

AIS is self-reported. A vessel can switch its transponder off, spoof a position, or simply lose signal in congested water. The ships most worth watching are often the ones that have gone dark.

What SAR adds

A Sentinel-1 radar pass images through cloud and darkness, and a metal hull returns a strong signal against calm water — so it reveals a vessel whether or not it is broadcasting AIS. Comparing SAR detections to AIS surfaces the dark ones.

All-Weather Detection

Sentinel-1 SAR sees vessels day or night and through cloud — when optical imagery cannot.

Dark Vessels

Detect ships regardless of AIS, then compare against a tracking feed to find the ones not reporting.

Chokepoints & Ports

Draw a strait, anchorage, or port and count vessels and activity over a defined area.

Monitor Over Time

Track an area as a time series so a change in vessel count surfaces as an anomaly automatically.

Maritime Signals

Overlay geolocated maritime event signals — incidents, naval movements — alongside the imagery.

No GIS Required

Runs in the browser. Draw an area and detect vessels without installing or scripting anything.

How It Works

Choose a maritime area

Draw a port, strait, anchorage, or stretch of coast you want to watch — no GIS software, just a polygon on the map.

Detect vessels in SAR

Run ship detection on Sentinel-1 radar, which images through cloud and at night and returns bright vessel returns against dark water — regardless of whether a vessel is broadcasting AIS.

Correlate with maritime signals

Overlay geolocated maritime event signals — incidents, chokepoint activity, naval movements — and read AI-enriched summaries to add context to what the imagery shows.

Watch it over time

Monitor the area as a time series so a change in vessel count or new activity surfaces as an anomaly, not something you have to catch by eye.

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 many sources — vessel tracking (AIS), radar, satellites, patrols, and intelligence — into one current picture of what is happening at sea.

What are dark vessels, and why do they matter?▼

A dark vessel is a ship that has switched off its AIS transponder, so it does not appear in conventional vessel-tracking feeds. Vessels go dark to conceal activities such as sanctions evasion, illegal, unreported, and unregulated (IUU) fishing, or unauthorized transfers. Because AIS is self-reported and can be turned off or spoofed, AIS gaps are exactly where satellite imagery earns its place.

How does SAR satellite imagery help?▼

Synthetic aperture radar (SAR) such as Sentinel-1 images day or night and through cloud, and metal hulls return a strong radar signal against the low backscatter of calm water. That means a SAR pass can reveal a vessel whether or not it is broadcasting AIS. Comparing what SAR detects against what is reporting AIS is the classic way to surface dark vessels.

Does Off-Nadir Delta ingest AIS feeds?▼

Off-Nadir Delta provides the satellite-imagery half of maritime domain awareness — SAR-based vessel detection, area monitoring over time, and maritime event signals — rather than a live AIS feed. The honest framing is that it shows you what the imagery sees, which is precisely the part AIS cannot tell you when a vessel goes dark. You can pair it with an AIS source of your choice to compare the two.

Who is satellite-based maritime awareness for?▼

It is built for coast guards and maritime agencies, fisheries and environmental enforcement, port and shipping analysts, sanctions and risk teams, journalists, and researchers investigating activity at sea. Anyone who needs to know what is happening in a stretch of water — and cannot rely on vessels to report themselves — is a candidate.

Is it free to start?▼

Yes — you can browse and explore for free, and a free tier is available once you sign in. Imagery rendering, ship detection, and area monitoring are metered with tokens, and some capabilities depend on your plan. See the pricing page for current details.