I am looking for a GeoTIFF raster marine chart

Introduction: What is a GeoTIFF raster marine chart?

Are you looking for a GeoTIFF raster marine chart to plan a voyage, use navigation software or access a digital representation of an official nautical chart? GeoTIFF is one of the formats used to provide georeferenced digital raster marine charts. It combines a chart image with geographical information so that the chart can be accurately positioned within compatible navigation software.

A raster marine chart works differently from a vector chart. It digitally reproduces the appearance of a paper chart: coastlines, soundings, depths, depth contours, lights, buoyage, landmarks, wrecks, hazards and other hydrographic information appear as graphic elements within the chart. The GeoTIFF format adds georeferencing information to the image, allowing the software to determine precisely where each part of the chart is located.

Nautic Way Maritime Bookshop offers digital raster GeoTIFF marine charts from hydrographic offices and specialist chart publishers. However, choosing a file should not be based on the format alone: the geographical area, chart reference, scale, coordinate system and compatibility with the navigation software are all essential considerations.

Raster marine chart vs. vector marine chart: what is the difference?

The main difference between raster and vector charts lies in the way cartographic information is stored.

A raster chart consists of a digital image. It corresponds to a graphical representation of the chart, similar to a highly accurate digital image of a paper chart, but enhanced with data allowing it to be georeferenced.

A vector chart consists of individual geographical objects: lines, points, areas, soundings, navigation aids, contours and other objects can be stored separately and displayed dynamically by the software.

Raster charts are therefore particularly useful when you want to preserve the cartographic presentation of a hydrographic office. They make it possible to retain the symbology, graphic layout and information as they appear on the original chart.

The choice between raster and vector depends primarily on the software being used, the type of navigation and the data available for the area concerned.

What is the GeoTIFF format?

GeoTIFF is a TIFF image format containing geographical information. This data can indicate the position of the image on Earth and its reference system.

In marine cartography, this means that a GeoTIFF raster chart can be accurately positioned within compatible navigation software.

Georeferencing is therefore a fundamental characteristic. A standard TIFF image without geographical information is not equivalent to a GeoTIFF marine chart intended for navigation.

Depending on the files and their producers, the associated information may include:

• the geographical position of the chart;

• the coordinate reference system;

• the map projection;

• the chart scale;

• the image resolution;

• parameters required to position the chart within compatible software.

It is therefore important to check the file specifications before using it.

What is a digital GeoTIFF raster marine chart used for?

A GeoTIFF marine chart can be used in different navigation and route-planning situations, provided that the software being used supports the format and that the file's terms of use allow it.

It can be used to:

• plan a maritime route;

• study a navigation area before departure;

• visualize coastlines and major hazards;

• prepare an offshore passage;

• work on remote or less frequently navigated areas;

• integrate raster cartography into compatible navigation software;

• complement route planning with several cartographic sources;

• retain a digital representation of an official chart.

For example, a sailor preparing an Atlantic crossing can use raster charts at different scales to progressively study the overall route, coastal approaches and port areas. Similarly, a sailor planning a Mediterranean voyage may need charts covering different regions and different levels of detail.

Raster charts are particularly useful for preserving a faithful representation of the chart produced by the hydrographic office.

SHOM GeoTIFF charts: official French hydrographic cartography

SHOM, the French Hydrographic and Oceanographic Service, produces official French nautical charts and nautical information. Some digital marine charts are available in raster format and can be used in compatible GeoTIFF environments, depending on the specific chart references and terms of use.

A SHOM GeoTIFF marine chart can contain the fundamental cartographic information represented on the corresponding chart: soundings, depths, hazards, wrecks, lights, buoyage, landmarks, depth contours and other information required to understand the maritime area.

The raster format preserves the graphical appearance of the SHOM chart, which can be particularly useful for sailors familiar with paper charts.

Available areas may include very different maritime regions, such as the English Channel, Atlantic Ocean, Mediterranean Sea, North Sea, Indian Ocean, Pacific Ocean and even certain polar regions, depending on the references available.

However, the exact chart reference and geographical coverage should always be checked. A broad geographical category does not necessarily mean that a single file covers an entire region.

Admiralty and other GeoTIFF raster charts

The principle of GeoTIFF raster charts is not limited to SHOM. Other hydrographic offices and nautical chart publishers also use georeferenced raster formats to distribute digital charts.

Admiralty charts, produced by the United Kingdom Hydrographic Office, are an important reference for many international maritime areas. Depending on the product and licensing conditions, digital cartographic data may be available in different formats.

To correctly identify a GeoTIFF raster chart, three elements should therefore be distinguished:

• the producer or hydrographic office;

• the chart reference;

• the format and technical terms of use.

A SHOM GeoTIFF chart and an Admiralty GeoTIFF chart may both be georeferenced raster charts, but they are not necessarily interchangeable. They may have different chart references, geographical coverage, coordinate systems or terms of use.

How do you choose a GeoTIFF marine chart?

The first criterion is the geographical area. Determine precisely where you will be sailing or which area you want to study.

The second criterion is scale. A chart intended for general navigation does not necessarily provide the same level of detail as a chart used for coastal approaches or port entrances.

The third criterion is the chart reference. It is important to check the exact chart number or identifier to avoid selecting a sheet covering a neighbouring area or providing insufficient detail.

The fourth criterion concerns the software. Not all navigation software handles GeoTIFF raster charts in the same way. Solutions such as Adrena, ScanNav or other charting software may support certain raster files, but compatibility should be checked for the specific version and file type concerned.

Finally, the file's licensing and terms of use must be checked.

GeoTIFF charts and navigation software

A GeoTIFF raster marine chart is not a universally compatible format for all electronic navigation equipment.

A file may be perfectly georeferenced and still not be accepted by a particular chartplotter or software application. Compatibility depends on the software, its version, the supported coordinate reference systems and the way in which the producer supplies the file.

Before use, it is therefore recommended to check:

• the navigation software being used;

• its version;

• supported raster formats;

• compatible coordinate reference systems;

• maximum or recommended resolution;

• any additional files required;

• licensing conditions.

This verification is particularly important when a chart is to be integrated into a professional navigation system or used to plan a complex voyage.

GeoTIFF raster charts for coastal and offshore navigation

The use of a raster chart also depends on the type of navigation.

For coastal navigation, chart accuracy and level of detail are essential. Port approaches, channels, shoals, wrecks, restricted areas and buoyage generally require cartography appropriate to the scale of navigation.

For offshore passages, the requirements may be different. A chart covering a large area allows the sailor to visualize the overall route and major ocean regions, while larger-scale charts become necessary as the vessel approaches the coast.

For example, during a circumnavigation, several levels of cartography may be required: general charts for planning, regional charts for ocean passages and detailed charts for coastal and port approaches.

Why use a raster chart rather than a simple image?

A simple chart image does not necessarily contain the information required to position it automatically within navigation software.

GeoTIFF provides precisely this geographical dimension. The software can use the georeferencing information to position the chart image at its real-world location.

This distinction is fundamental for digital navigation. The sailor is not simply looking for a visual reproduction of a chart: they need a representation that is correctly positioned within their electronic charting environment.

GeoTIFF therefore provides an interesting combination of graphical fidelity and digital usability, particularly when working with the raster representation of an official chart.

Limitations of a GeoTIFF raster marine chart

A raster chart should not be considered a universal solution.

Compared with vector data, raster charts have certain limitations: the image has a defined resolution, and readability may decrease when zooming in significantly. Cartographic objects cannot necessarily be manipulated individually in the same way as they can within a vector database.

Furthermore, a digital chart never eliminates the need for the navigator to check up-to-date nautical information, Notices to Mariners, weather conditions, tides, currents and other information required for safe navigation.

Electronic charting should remain one element of a comprehensive navigation and voyage-planning process.

Example: planning an ocean passage with GeoTIFF charts

Imagine a sailing vessel preparing to cross from Europe to the Caribbean.

A small-scale GeoTIFF raster chart can be used to study the overall route between Europe, the Canary Islands, Cape Verde and the Caribbean. As the vessel approaches the coast, larger-scale charts become necessary to prepare approaches, identify hazards and study channels and port areas.

The same principle applies to navigation in the Mediterranean, Indian Ocean or Pacific: geographical coverage and scale must correspond to each stage of the voyage.

Conclusion

A GeoTIFF raster marine chart is a particularly useful digital charting solution for sailors who want to use a georeferenced representation of an official nautical chart within compatible software. It combines the graphical fidelity of a raster chart with the geographical information required for accurate digital positioning.

Whether it is a SHOM GeoTIFF marine chart, an Admiralty chart or another raster chart, the choice should always take into account the navigation area, chart reference, scale, coordinate reference system, software being used and licensing conditions.

Nautic Way Maritime Bookshop offers a selection of digital GeoTIFF raster marine charts for sailors looking for accurate, georeferenced digital cartography adapted to their navigation environment.

FAQ – GeoTIFF raster marine charts

What is a GeoTIFF raster marine chart?

A GeoTIFF raster marine chart is a digital nautical chart consisting of a georeferenced image. It reproduces the graphical representation of a marine chart and contains information allowing compatible software to position it accurately.

What is the difference between a GeoTIFF chart and a vector chart?

A GeoTIFF raster chart is a georeferenced image, whereas a vector chart consists of individual geographical objects. Raster therefore reproduces the original chart's appearance very faithfully, while vector data allows more dynamic management of individual cartographic objects.

Can a SHOM GeoTIFF chart be used with navigation software?

Yes, provided that it is compatible with the software and its version. Navigation and charting software such as Adrena or ScanNav can support certain raster formats, but exact compatibility with the specific file must always be checked.

Does a GeoTIFF marine chart work with all GPS units and chartplotters?

No. GeoTIFF is not universally supported by all GPS units, chartplotters and electronic navigation systems. You must check which formats are supported by the specific equipment and software.

Is a GeoTIFF raster chart georeferenced?

Yes. The principle of GeoTIFF is precisely to associate an image with geographical information allowing it to be positioned accurately. However, the exact georeferencing parameters and coordinate reference systems used should be checked for each file.

Which GeoTIFF chart should I choose for an Atlantic crossing?

You should choose the references that precisely cover the planned navigation areas, taking into account the required scale and level of detail. A small-scale chart may be suitable for overall planning, while larger-scale charts will be necessary for coastal approaches.

Are there SHOM GeoTIFF charts covering foreign waters?

Some SHOM chart references cover maritime areas far beyond the French coastline. However, coverage depends on the specific chart reference. The exact geographical area covered by each chart should therefore be checked.

Does a GeoTIFF raster chart replace a paper chart?

It provides a digital representation of the chart and can be used in a compatible electronic environment. For navigation, however, it remains necessary to use up-to-date nautical information and appropriate procedures and equipment for the type of navigation being undertaken.

What scale should I choose for a GeoTIFF raster marine chart?

The scale depends on the intended use. A small scale is suitable for representing large areas and planning an overall route. A large scale provides more detail for coastal navigation, channels and port approaches.

Does a GeoTIFF chart contain tide and weather information?

Not necessarily. A marine chart contains the cartographic information represented on the specific chart. Weather forecasts, tides, currents and Notices to Mariners should be obtained from the appropriate sources and services.

Why choose a GeoTIFF raster chart for navigation?

Its main advantage is that it provides a georeferenced digital representation that preserves the appearance and symbology of an official chart. It can be particularly useful in navigation and charting software that supports this format.