While most people could name famous warships or ocean liners, hardly anyone could identify the state body that actually makes safe navigation possible. Yet France has run one such service, uninterrupted, since before the birth of the United States – and yes, it is older than Britain’s.
France’s hidden maritime record
The institution is the SHOM, short for “Service hydrographique et océanographique de la Marine”. It sits under the French Ministry of the Armed Forces and has just passed a striking milestone: 305 years of continuous operation.
Founded in 1720 as the “Dépôt des cartes et plans de la Marine”, SHOM is now recognised as the oldest official hydrographic service on the planet still in activity. Britain’s famed UK Hydrographic Office, by comparison, dates from 1795.
For 305 years, France has maintained the same core mission at sea: know the ocean accurately, and act from a position of strength.
That longevity is not just a curiosity for naval historians. It underpins how France manages one of the largest maritime domains on Earth: around 11 million square kilometres of exclusive economic zone (EEZ), spread from the Caribbean to the Indian and Pacific Oceans.
What SHOM actually does
Behind the acronyms and dates lies a very concrete job. SHOM’s data feed commercial shipping, fishing fleets, energy companies, coastal planners and the French Navy.
- National hydrography: measuring depths, mapping seabeds, locating reefs, wrecks and sandbanks, and producing official nautical charts.
- Support to defence: providing precise information for submarine routes, amphibious operations, mine warfare and weapon systems that depend on detailed knowledge of seabed shape.
- Public policy support: helping authorities monitor erosion, plan sea defences, assess flood risks and prepare for rising sea levels linked to climate change.
Without this, there would be fewer safe ports, more accidents in shallow waters and much weaker control over offshore resources.
Three centuries of hydrography: France vs the rest
Hydrographic services exist in all major maritime countries, but almost none can point to such a long, unbroken institutional line. A brief comparison shows how early France moved.
| Country | Hydrographic service | Year created | Continuity | Notable feature |
|---|---|---|---|---|
| France | SHOM | 1720 | Uninterrupted | Oldest official hydrographic service still active |
| United Kingdom | UK Hydrographic Office | 1795 | Continuous | Key to Royal Navy’s global expansion |
| United States | NOAA / Office of Coast Survey | 1807 | Continuous, with reforms | Strongly science-driven, with a civil focus |
Several turning points reshaped SHOM over time without breaking that thread. In 1886, it officially became the Hydrographic Service of the Navy. In 1971, it absorbed oceanography, moving beyond mere charts to currents, tides and physical properties of seawater. Then in 2007, it turned into a public administrative body, with more modern governance but the same strategic role.
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From copper plates and ink to AI and underwater drones, the French hydrographic service has updated its tools while keeping its original purpose.
Drones and data: a quiet technological leap
Robots on and under the waves
The job of mapping 11 million km² of sea is impossible with crewed ships alone. That is why SHOM has started to invest heavily in autonomous platforms.
Recent acquisitions include two high-tech systems:
- DriX H-9: an autonomous surface drone built by French firm Exail, designed to scan seabeds with high precision while consuming less fuel and requiring fewer crew.
- NemoSens: a compact underwater micro-drone from RTSys, ideal for shallow continental shelves and coastal zones where larger ships struggle.
The DriX H-9 can work alone over large areas, or in tandem with a traditional hydrographic ship. While the crewed vessel handles complex operations, the drone sweeps the surrounding zone and sends back dense bathymetric data. NemoSens, much smaller, can slip into tight spaces, near offshore structures or sensitive ecosystems.
They join an expanding robotic fleet that already includes another DriX, the H-8 “Marlin”, delivered in 2025, and will soon welcome a deep-diving autonomous underwater vehicle, the Hugin Superior, rated to 6,000 metres and built by Kongsberg Discovery in Norway.
From occasional surveys to continuous monitoring
This shift marks a change in philosophy. Instead of sending ships on occasional missions to update charts every few years, SHOM wants near-continuous data streams over wide areas.
That requires not just robots, but also powerful processing tools. The organisation is deploying artificial intelligence to sort through huge volumes of sonar and sensor readings, automation to clean and validate bathymetric data, and predictive models to anticipate how seabeds and shorelines might change.
The real revolution is less about shiny drones than about what they feed: a constantly updated, strategic picture of the ocean around France.
Maritime data as a sovereignty tool
The stakes go far beyond navigation safety. Undersea cables, which carry the majority of global internet traffic, sit on the seabed that SHOM maps. Offshore wind farms, fishing grounds, gas fields and potential deep-sea minerals all lie within the French EEZ.
In that setting, relying on foreign data can become a vulnerability. When tension flares in a region, states want their own measurements and models, not approximations from a commercial provider based elsewhere.
Hydrographic data help France:
- Prove the extent of its maritime zones in legal disputes.
- Plan and secure cable routes and energy projects.
- Support naval deployments with precise seabed knowledge.
- Assess coastal risk for cities, ports and industrial sites.
Specialist vessels also enter the picture here. France, for instance, owns a large share of the world’s fleet of cable ships, used to lay and maintain those crucial data arteries on the seafloor. SHOM’s charts and models are part of that broader toolbox of influence.
Key terms that quietly shape policy
What is an EEZ, exactly?
The exclusive economic zone, or EEZ, is a concept set out under the UN Convention on the Law of the Sea. It extends up to 200 nautical miles from a country’s coastline, or from its overseas territories.
Within this area, the coastal state has special rights to exploit natural resources in the water column, on the seabed and beneath it. That does not mean full sovereignty like on land, but it does grant control over fishing, energy and mining activities.
France’s scattered territories – from New Caledonia to Réunion and French Guiana – give it the second-largest EEZ on the planet, behind the United States. SHOM helps define and document those boundaries.
Why “bathymetry” matters
Bathymetry is simply the measurement of depths in oceans, seas and lakes. A bathymetric chart is the underwater equivalent of a topographic map on land.
Accurate bathymetry is crucial for:
- Submarines that must avoid seamounts, canyons or shallow ridges.
- Large container ships with deep draughts approaching ports.
- Predicting how tsunamis or storm surges will propagate over coastal shelves.
- Designing pipelines or cables that lie on the seabed.
Poor data can mean accidents, higher insurance costs and weaker crisis response when something goes wrong at sea.
Practical implications for everyday life
For most citizens, SHOM’s work never appears on a smartphone screen. Yet its influence pops up in unexpected places. When a ferry route is rerouted after a sandbank shifts, when coastal flood maps change after an updated storm-surge model, or when a new offshore wind farm site is chosen, hydrographic data sit in the background.
Imagine a future coastal city faced with rising seas and more intense storms. Planners will need to decide where to build barriers, where to retreat and which ports to reinforce. Their options depend on fine-grained understanding of seabed slopes, sediment movements and wave patterns. That is exactly the type of long-term record a 305-year-old service can provide.
There are risks, too. As more ocean monitoring becomes digital and autonomous, data security and system resilience become as vital as the measurements themselves. A hacked or spoofed chart can be as dangerous as a reef. France’s push to keep this capability under state control reflects that concern.
For students, sailors, tech companies and policymakers alike, the lesson is straightforward: what happens under the surface – in terms of data, charts and measurements – can shape trade routes, naval strategy and even local housing plans more than any spectacular ship on the horizon.
Originally posted 2026-03-06 22:31:57.