SHOM Raster GeoTIFF Marine Charts – Atlantic Ocean

Introduction

SHOM raster GeoTIFF marine charts of the Atlantic Ocean are georeferenced digital marine charts designed for the preparation, analysis and visualization of Atlantic maritime areas in a compatible computer environment. They provide digital access to raster marine cartography while retaining the geographical information required for accurate positioning.

The Atlantic Ocean is a major maritime area for global navigation. It covers a vast region between Europe, Africa and the Americas, from northern to southern latitudes. It includes very different navigation environments: ocean crossings, coastal navigation, port approaches, archipelagos, tropical regions and transatlantic routes.

In this context, a SHOM digital marine chart in GeoTIFF format can be used to prepare a route, analyse a geographical area or integrate raster cartography into compatible navigation software. It can be relevant to recreational sailors, offshore sailors, long-distance cruisers, maritime professionals, training organizations, scientific vessels and users of digital charting systems.

What is a SHOM raster GeoTIFF marine chart?

A raster marine chart is a digital representation of a nautical chart in the form of a georeferenced image. It therefore preserves the graphical appearance of the original cartography, including the various symbols and hydrographic information shown on the chart.

Depending on the reference concerned, a raster marine chart may include:

• soundings and depths;

• bathymetric contours;

• coastlines;

• shoals;

• rocks and hazards;

• charted wrecks;

• lights and navigation aids;

• buoys and marks;

• hydrographic information;

• specific areas or limits.

The GeoTIFF format combines the chart image with georeferencing information that allows it to be correctly positioned on the Earth's surface.

This feature is essential when using the chart with navigation software. A simple TIFF or JPEG image can visually represent a chart, but it does not necessarily contain the data required for automatic geographical positioning.

Why use a SHOM digital marine chart in the Atlantic Ocean?

The Atlantic is an extremely vast ocean. Appropriate chart preparation is therefore essential, particularly when a voyage involves several thousand nautical miles.

A SHOM raster GeoTIFF marine chart can be used to:

• prepare an Atlantic crossing;

• study a route between Europe and the Caribbean;

• analyse an area before offshore navigation;

• prepare navigation along Atlantic coasts;

• study approaches to an archipelago or port;

• analyse charted depths and hazards;

• integrate digital cartography into compatible software.

Digital charting makes preparation on land easier. It allows the navigator to study an overall route, identify areas requiring more detailed cartography and prepare the different stages of an ocean voyage.

What geographical coverage is available for the Atlantic Ocean?

The Atlantic Ocean covers an immense area between Europe, Africa and the Americas.

The exact coverage of a SHOM GeoTIFF chart nevertheless depends on its chart reference. It is therefore essential to check the area covered by the file before using it to prepare navigation.

Depending on the chart references available, Atlantic cartography may concern different sectors:

• North Atlantic;

• Northeast Atlantic;

• European coasts;

• French coasts;

• Iberian Peninsula coasts;

• African coasts;

• tropical Atlantic;

• Caribbean and West Indies;

• South Atlantic;

• approaches to Atlantic archipelagos.

A chart covering a large area does not necessarily provide the level of detail required for a coastal approach. The choice of chart reference, scale and geographical area must therefore be adapted to the type of navigation planned.

Example: preparing a transatlantic crossing

Consider a sailing yacht preparing a crossing between the European coast and the Caribbean.

Preparation can begin with cartography covering a sufficiently large area to display the entire route.

The navigator can then progressively analyse:

1. the departure area;

2. departure from the coastal area;

3. the ocean route;

4. possible stopovers or diversion areas;

5. the approach to the Caribbean;

6. the destination and its approaches.

This approach makes it possible to distinguish between the cartography required for general route planning and that required for coastal navigation.

Close to the coast, a larger-scale chart may be necessary to provide an appropriate level of detail for approaches, channels, shoals and hazards.

Coastal navigation and offshore navigation

One of the advantages of digital charting is the ability to work at different stages of navigation planning.

For an ocean crossing, the navigator primarily needs an overall view of the route and the maritime areas being crossed.

For coastal navigation, requirements are different. Cartographic accuracy becomes particularly important when approaching ports, navigating channels, straits and areas where navigation becomes confined.

A general marine chart of the Atlantic Ocean should therefore not be considered sufficient for every stage of a voyage. The required level of detail depends directly on the area and intended use.

Raster GeoTIFF or vector chart?

A raster GeoTIFF chart and a vector chart are two different digital charting technologies.

Raster reproduces a georeferenced image of the chart. It retains the graphical presentation, symbols, text, colours, soundings and bathymetric contours.

Vector cartography stores individual geographical objects as separate data. The software can then interpret a depth, buoy, coastline or area individually.

Raster has the particular advantage of preserving a representation close to that of traditional marine cartography. It can be particularly useful for users who want to work with georeferenced graphical cartography in a compatible computer environment.

The choice depends on the software being used, the type of navigation planned and the available data.

Using the chart with navigation software

A SHOM GeoTIFF marine chart is not universally compatible with all navigation software.

Certain software applications, including Adrena or ScanNav, can use some georeferenced raster data. Compatibility nevertheless depends on the file, its technical characteristics and the software version.

Before using a SHOM digital raster GeoTIFF marine chart, it is recommended to check:

• the exact chart reference;

• the geographical area covered;

• the scale;

• the resolution;

• the coordinate reference system;

• the map projection;

• the file format;

• compatibility with the software being used;

• licensing and terms of use;

• information relating to updates where applicable.

The GeoTIFF format alone therefore does not guarantee compatibility.

GeoTIFF marine charts and transatlantic navigation planning

For an Atlantic crossing, charting is an essential component of preparation, but it must be combined with the other data required for navigation.

The navigator can study:

• possible routes;

• coastal navigation areas;

• depths and hazards;

• currents;

• weather conditions;

• prevailing winds;

• swell;

• shipping traffic areas;

• port approaches;

• up-to-date nautical information.

Cartography represents the geography and hydrography of an area, but it does not replace the meteorological and operational information required for actual navigation.

How to choose a SHOM raster GeoTIFF chart of the Atlantic?

Several criteria should be checked before selecting a SHOM digital GeoTIFF marine chart.

Geographical coverage

First, check that the chart reference covers the exact area required. A general chart may cover a very large part of the Atlantic without necessarily being suitable for local navigation.

Scale

The scale should correspond to the intended use. A small-scale chart allows a large area to be displayed, while a large-scale chart provides more detail for coastal navigation.

Computer compatibility

The software being used must be capable of reading and correctly positioning the GeoTIFF file.

Coordinate reference system

The georeferencing information must be compatible with the charting environment being used.

Navigation context

A transatlantic crossing, coastal navigation and a port approach do not require the same level of cartographic detail.

Cartography must be supplemented by nautical information

A digital marine chart, even a detailed one, does not by itself constitute all the information required for navigation.

When preparing navigation in the Atlantic Ocean, it is necessary to take into account current information concerning:

• changes to navigation aids;

• newly reported hazards;

• temporary restrictions;

• marine works;

• weather conditions;

• currents and tides;

• regulated areas;

• Notices to Mariners and other navigational information.

The GeoTIFF chart therefore provides a digital cartographic foundation that should be integrated into a broader navigation planning process.

Conclusion

SHOM raster GeoTIFF marine charts of the Atlantic Ocean provide a georeferenced digital charting solution for preparing and analysing Atlantic navigation in a compatible software environment.

The raster format preserves a graphical representation close to that of a traditional marine chart, while GeoTIFF provides accurate geographical positioning.

This type of charting can be used to prepare an Atlantic crossing, analyse a coastal area or study the different stages of an offshore voyage. The choice of chart reference, geographical coverage and scale nevertheless remains critical.

For both transatlantic crossings and coastal navigation, cartography should be supplemented by the meteorological, nautical, regulatory and operational information required for navigation.

FAQ – SHOM Raster GeoTIFF Marine Charts of the Atlantic Ocean

What is a SHOM raster GeoTIFF marine chart of the Atlantic Ocean?

It is a georeferenced digital marine chart representing SHOM cartography in raster format for a specific area of the Atlantic Ocean. The GeoTIFF format combines the chart image with the data required for geographical positioning.

What is a SHOM digital GeoTIFF marine chart of the Atlantic used for?

It can be used to prepare a transatlantic crossing, study an ocean route, analyse a maritime area or integrate raster cartography into compatible navigation software.

Does a SHOM GeoTIFF chart cover the entire Atlantic Ocean?

This depends on the chart reference. Each chart has specific geographical coverage and scale. The covered area must therefore be checked before use.

Can a GeoTIFF chart be used to prepare an Atlantic crossing?

Yes. An appropriate chart can be used to prepare a transatlantic route and analyse the different areas crossed. It must nevertheless be supplemented by the meteorological, nautical and operational information required for navigation.

Is a general marine chart of the Atlantic sufficient for coastal navigation?

Not necessarily. A general chart may be suitable for planning an ocean route, but coastal navigation or a port approach generally requires more detailed charting.

Can a SHOM GeoTIFF chart be used with Adrena?

Adrena can use certain georeferenced raster data. Compatibility should nevertheless be checked for the SHOM reference, GeoTIFF file and software version being used.

Is a SHOM GeoTIFF chart compatible with ScanNav?

ScanNav can use certain georeferenced raster data. The exact compatibility of the file and software version should be checked.

What scale should be used for a marine chart of the Atlantic Ocean?

The scale depends on the intended use. A small scale allows a large part of the ocean to be displayed, while a larger scale is more suitable for detailed study of coasts, channels, ports and confined navigation areas.

Does a GeoTIFF chart provide weather information?

No. A marine chart primarily represents the cartographic and hydrographic information associated with its reference. Weather conditions, winds, swell and currents must be obtained from appropriate and up-to-date data sources.

Why should the SHOM chart reference be checked before using a GeoTIFF chart?

Because each reference has its own geographical coverage, scale and level of detail. A chart suitable for an ocean crossing does not necessarily provide the precision required for coastal navigation.

Can a SHOM raster GeoTIFF chart be used for professional navigation in the Atlantic?

It can form part of the cartographic preparation and analysis for certain professional uses, subject to the coverage, scale, software compatibility and terms of use of the file. It should be integrated into all applicable navigation procedures and data for the vessel and operation concerned.