Shom L Nautical Chart – Indian Ocean

Shom L Indian Ocean nautical chart: paper cartography for navigation in the Indian Ocean

The Shom L Indian Ocean nautical chart is a folded paper nautical chart designed for planning and conducting navigation in the different areas of the Indian Ocean covered by Shom cartography. It can be used to plan a route, study a passage, identify coastlines, islands, reefs, shoals, channels, anchorages and harbour approaches.

The main characteristic of the Shom L chart is its compact format. Folded to A4 size, approximately 21 × 29.7 cm, it unfolds into a large-format chart of approximately 84 × 119 cm, corresponding to an A0 format. Shom L charts are printed on 150 g/m² paper.

This format is particularly useful for navigators who need to transport or store several nautical charts. In the Indian Ocean, voyages may connect widely separated areas such as Madagascar, Réunion Island, Mauritius, Mayotte, the Seychelles or the French Southern and Antarctic Lands. The compact storage of a folded chart makes it easier to organise nautical documentation on board.

Shom L cartography covers areas including Madagascar, Réunion Island, Mauritius, Tromelin, the Glorioso Islands and other sectors of the Indian Ocean. Available references also cover different scales, from charts intended for regional navigation to much more detailed charts for coastal areas and harbour approaches.

A nautical chart suitable for navigation in the Indian Ocean

The Indian Ocean presents considerable geographical diversity. It includes continental coastlines, large islands, archipelagos, coral reefs, passes, lagoons and vast ocean areas.

Navigation between Madagascar and the Mascarene Islands does not require the same cartographic information as an approach to Port Louis, Saint-Denis on Réunion Island, Mamoudzou or a coastal anchorage.

The Shom L chart provides a paper representation suitable for different stages of navigation planning.

For offshore navigation, a chart covering a large area can be used to prepare the general route. When approaching a coast, island or harbour, a larger-scale chart becomes necessary in order to study soundings, hazards, passes, channels and harbour facilities.

Planning a voyage in the Indian Ocean therefore often requires several levels of cartography depending on the distance travelled and the areas visited.

Madagascar: a major area of Shom cartography

Madagascar is one of the main areas covered by Shom charts in the Indian Ocean.

This very large island has very different coastal configurations in the north, east, west and south. Navigators may be concerned with approaches to Nosy Be, Antsiranana, Toamasina, Morondava, Toliara or Sainte-Luce.

The northwest coast includes areas around Nosy Be, Cape Ambre and Antsiranana Bay. One Shom L reference, for example, covers the area from Nosy Be to Antsiranana Bay, including the Geyser Reef and the Glorioso Islands. This chart is supplied in folded format and has a scale of approximately 1:349,400.

The east coast of Madagascar also includes numerous charted areas, including Sainte-Marie, Tamatave, Mananjary and various coastal anchorages.

In the south, the areas around Toliara, Saint-Augustin Bay and Cape Sainte-Marie also require cartography appropriate to the scale and type of navigation.

Réunion Island, Mauritius and Tromelin

The Mascarene Islands form another important navigation area in the Indian Ocean.

Réunion Island is charted around Saint-Denis, Le Port and various areas along the island's coast. Mauritius, with Port Louis, is a major stopover for navigation in the southwest Indian Ocean.

A Shom L reference, 7349L, covers the area from Réunion Island to Mauritius and also includes Tromelin Island. It is presented in folded format, with an unfolded A0 size and a scale of approximately 1:349,800.

For navigation between Réunion Island and Mauritius, this regional coverage can be used to plan the route between the two islands. Additional larger-scale charts may then be required to study in detail the approaches to Saint-Denis, Le Port, Port Louis or other coastal areas.

Mayotte, the Comoros and the Glorioso Islands

The northwestern Indian Ocean also includes the Comoros, Mayotte and several associated islands and reefs.

Mayotte, with Mamoudzou as its main port centre, has a maritime environment characterised by reefs, passes, a lagoon and numerous coastal areas.

In this type of environment, chart scale is particularly important. A regional chart allows the archipelago to be positioned within its wider geographical setting, while a more detailed chart is required for a harbour approach or navigation within a lagoon.

The Glorioso Islands are also a distinctive area for navigation in the northwestern Indian Ocean. They are included, for example, in the coverage of a Shom L chart covering the area from Nosy Be to Antsiranana Bay.

Seychelles and archipelago navigation

The Seychelles are another characteristic maritime environment in the Indian Ocean. The archipelago consists of numerous islands, reefs and navigation areas that require careful interpretation of nautical charts.

Victoria, on Mahé Island, is the principal port and maritime centre of the Seychelles. Navigators may also be concerned with approaches to Praslin, La Digue and other islands in the archipelago.

In an island environment, the nautical chart is particularly useful for identifying soundings, reefs, isolated dangers, channels and represented anchorage areas.

Planning a voyage between Madagascar, the Comoros, the Seychelles and the Mascarene Islands therefore requires distinguishing between regional coverage charts and charts intended for detailed coastal navigation.

Information shown on a Shom L Indian Ocean nautical chart

Depending on the geographical area and scale, a Shom L nautical chart may show a wide range of information useful for navigation:

• soundings and depths;

• depth contours;

• seabed characteristics where represented;

• reefs and shoals;

• rocks;

• wrecks;

• maritime aids to navigation;

• lights and light characteristics;

• landmarks;

• channels and passes;

• ports and harbour facilities;

• anchorages;

• regulatory limits and restricted areas;

• maritime infrastructure;

• information required for route planning;

• insets providing a more detailed representation of certain areas.

These features are particularly important in the Indian Ocean, where navigators may move quickly from ocean navigation to coastal navigation or reef environments.

The importance of scale for an Indian Ocean nautical chart

Scale is an essential consideration when choosing a Shom L chart.

A small-scale chart can represent a large maritime area. It is suitable for general offshore route planning and visualising distances between islands and archipelagos.

A large-scale chart represents a smaller area with considerably more detail. It is particularly useful for harbour approaches, channels, passes, anchorages and complex coastal areas.

The Shom Indian Ocean catalogue therefore includes different scale categories, from coastal areas to oceanic areas. The Shom C Indian Ocean category currently referenced by Nautic Way includes coastal, littoral, offshore and oceanic charts.

For a passage between two islands, a regional chart may be suitable for general planning. For entering a harbour or passing through a reef pass, a much more detailed chart is generally required.

Comparison of Shom C, L, G, Z and Raster charts

Chart type	Support	Presentation	Main characteristic	Main use
Shom C	Paper	Flat, generally rolled	Large-format nautical chart	Route planning, chart table, coastal and offshore navigation
Shom L	Paper	Folded A4	Large format when unfolded, compact storage	Coastal navigation, passage planning, cruising and onboard transport
Shom G	Paper	Folded A4	Additional sedimentological and seabed information	Seabed study, fishing and specialised uses
Shom Z	Paper	Flat, generally rolled	Overlay showing exercise and firing areas	Identification of areas concerned by military activities
Shom Raster	Digital	Digital file	Georeferenced reproduction of a nautical chart	Use with compatible navigation and cartography software

The Shom L is therefore mainly distinguished by its folded format. Shom G charts provide additional sedimentological information about the nature and distribution of seabed sediments. Shom Z charts include an additional overlay concerning exercise and firing areas.

Shom Raster charts are digital representations of paper nautical charts intended for compatible software. In the Indian Ocean, highly detailed Raster charts are also available for harbour areas; for example, one reference covering the port and approaches of Toamasina is available at a scale of 1:15,000.

Shom L or Shom C for navigation in the Indian Ocean?

The choice between a Shom L and a Shom C mainly depends on the preferred method of storage and consultation.

The Shom C is a flat paper chart, generally rolled. It is particularly suitable when a large chart table allows the chart to remain open.

The Shom L is folded to A4 size. It is therefore more compact when stored and easier to transport in a chart portfolio.

This difference can be useful during a long voyage in the Indian Ocean. A voyage between Madagascar, Réunion Island, Mauritius, the Seychelles or the Comoros may require several charts covering different areas and scales.

The folded format makes it easier to organise the charts corresponding to the different stages of the voyage.

The Shom L as a route-planning tool

A paper chart makes it possible to visualise a route over a substantial geographical area.

Before an Indian Ocean passage, it can be used to study the position of islands, distances between stopovers, alternative routes and areas requiring particular attention.

It can also be used to prepare approaches to ports such as Saint-Denis, Le Port, Port Louis, Mamoudzou, Victoria, Antsiranana, Nosy Be or Toamasina.

A paper chart can therefore complement the electronic navigation systems used on board. It provides a geographical representation independent of the screen and facilitates certain stages of route planning.

Choosing a Shom L Indian Ocean nautical chart

Before selecting a Shom L nautical chart for the Indian Ocean, several criteria should be checked:

• the exact geographical area;

• the chart number;

• the title;

• the scale;

• the geographical coverage;

• the ports concerned;

• the islands and archipelagos covered;

• the passes and channels to be studied;

• the relevant anchorage areas;

• the type of navigation planned;

• the edition and update status.

This verification is particularly important in the Indian Ocean because of the size of the region. A chart covering Madagascar does not necessarily meet the same requirements as a chart covering the Mascarene Islands or a harbour approach.

Cartography adapted to different types of navigation

The Shom L Indian Ocean nautical chart can be used in a wide range of situations:

• offshore navigation;

• passages between islands;

• coastal navigation;

• cruising through archipelagos;

• harbour approach planning;

• navigation around Madagascar;

• navigation between Réunion Island and Mauritius;

• navigation around Mayotte and the Comoros;

• navigation around the Seychelles;

• study of anchorage areas;

• planning routes between the Mascarene Islands and Madagascar.

The diversity of the Indian Ocean environment makes the choice of scale and geographical coverage particularly important.

Conclusion

The Shom L Indian Ocean nautical chart is a paper resource particularly suited to navigators who want detailed cartography in a compact and easily transportable format.

Folded to A4 size and unfolding to approximately 84 × 119 cm, it combines a large cartographic surface with practical storage. It can support coastal navigation, regional passages and route planning across the different areas of the Indian Ocean.

Madagascar, Nosy Be, Antsiranana, Toamasina, Toliara, Réunion Island, Saint-Denis, Le Port, Mauritius, Port Louis, Tromelin, Mayotte, Mamoudzou, the Glorioso Islands and the Seychelles illustrate the diversity of areas that may be covered by Shom cartography in this region. Current Shom L references include, among others, a chart covering the area between Réunion Island and Mauritius and a chart covering Nosy Be, Antsiranana Bay, the Geyser Reef and the Glorioso Islands.

When selecting a Shom L Indian Ocean nautical chart, it is essential to check the chart number, scale, geographical coverage and intended type of navigation.

FAQ – Shom L Indian Ocean nautical charts

What is a Shom L Indian Ocean nautical chart?

It is a Shom paper nautical chart presented in a folded format and covering, depending on the reference, different areas of the Indian Ocean. It may cover Madagascar, Réunion Island, Mauritius, Tromelin, Mayotte, the Glorioso Islands or other areas of the region.

What is the format of a Shom L chart?

A Shom L chart is folded to A4 size, approximately 21 × 29.7 cm. When fully unfolded, it measures approximately 84 × 119 cm, corresponding to A0 size.

Which areas of the Indian Ocean are covered by Shom L charts?

Depending on the reference, coverage includes Madagascar, Réunion Island, Mauritius, Tromelin, the Glorioso Islands and different areas of the Indian Ocean.

Is there a Shom L chart covering the area between Réunion Island and Mauritius?

Yes. One Shom L reference covers the area between Réunion Island and Mauritius and also includes Tromelin Island.

Are there Shom L charts for Madagascar?

Yes. Several Shom charts cover different parts of the Malagasy coastline, including the northern, eastern, western and southern areas of Madagascar.

Which ports may be covered by Shom Indian Ocean charts?

Depending on the reference, charted areas may include Saint-Denis and Le Port on Réunion Island, Port Louis in Mauritius, Mamoudzou in Mayotte, Victoria in the Seychelles, and Antsiranana, Nosy Be and Toamasina in Madagascar.

Why is scale important for an Indian Ocean nautical chart?

A small-scale chart allows navigation planning over a large area, whereas a large-scale chart provides more detail for a coastline, harbour, channel, pass or anchorage.

What is the difference between a Shom L and a Shom C?

The Shom L is folded to A4 size and is therefore compact when stored. The Shom C is a flat paper chart, generally rolled. When unfolded, however, Shom L charts provide a large cartographic surface.

What is the difference between a Shom L and a Shom G?

The Shom L is a conventional nautical chart. The Shom G provides additional sedimentological information allowing the nature and distribution of seabed sediments to be studied.

What is a Shom Z chart?

A Shom Z, also called a Zonex chart, is a nautical chart with an additional overlay identifying exercise and firing areas associated with military activities.

What is a Shom Raster chart in the Indian Ocean?

It is a georeferenced digital version of a Shom nautical chart intended for compatible cartography and navigation software. Raster references are available for certain harbour areas in Madagascar.

Can a Shom L chart be used for an Indian Ocean crossing?

Yes, depending on its coverage and scale. For a long passage, several charts may nevertheless be required to cover the general route, the different regions crossed and approaches to ports or islands.

Is a Shom L suitable for navigation around Madagascar?

Yes. Several Shom references cover the Malagasy coastline at different scales, allowing both regional navigation and coastal approaches to be planned.

How do you choose a Shom L chart for the Indian Ocean?

Check the chart number, title, scale, geographical coverage, ports and islands covered, as well as the type of navigation planned. For complex navigation or a long passage, several charts at different scales may be required.