Shom raster nautical chart Planisphere
The Shom raster GeoTIFF marine charts for the world map are the digital versions of the official paper nautical charts, georeferenced for computer use. They are produced from the official data of the French Hydrographic and Oceanographic Service (Shom). They retain the exact visual appearance of traditional charts — colors, symbols, and bathymetry. Available in GeoTIFF format (300 dpi), they are compatible with navigation and GIS software such as OpenCPN, QGIS, and ArcGIS.
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Shom raster nautical chart Planisphere
Shom raster digital charts are provided in GeoTIFF format, with a standard resolution of 300 dpi. They are generated from the official paper nautical charts and faithfully reproduce their content, symbology, and layout.
Format and Technical Specifications
Format: GeoTIFF compliant with TIFF 6.0 standard, with embedded geographic tags.
- Projection: Mercator or Lambert depending on the source chart, using the WGS84 geodetic reference system (EPSG:4326) or a specific local projection.
- Resolution: 300 dpi (approximately 0.085 mm/pixel on the original paper chart).
- Metadata: embedded in the file (extent, georeferencing coordinates, projection system, scale).
- Average file size: varies depending on the paper chart format, generally from 50 to 200 MB per chart.
Software Compatibility
The GeoTIFF format is supported by several navigation software packages and GIS (Geographic Information Systems):
- Navigation software: OpenCPN, …
- GIS: QGIS, ArcGIS, MapInfo, Global Mapper…
- Other uses: integration into cartographic visualization systems, overlay with vector layers (bathymetric data, AIS, weather, regulated areas).
Use Cases and Regulatory Limitations
- Recreational boating (< 24 m): Shom GeoTIFF raster charts are recognized as equivalent to paper charts and meet the carriage requirements of French regulations.
- Professional navigation (> 24 m): These charts are considered navigation aids only. Vessels subject to SOLAS regulations must use ENC (Electronic Navigational Charts, S-57/S-101) on an approved ECDIS.
- Updates: Unlike vector ENCs, GeoTIFF raster charts do not benefit from incremental updates. Users must download new editions or corrected versions published by Shom.
Advantages and Limitations
- Advantages: broad compatibility with software, identical readability to the paper chart, easy integration into a GIS environment.
- Limitations: no native interactivity (no clickable objects, unlike ENCs), need to download new files for each update, regulatory constraints for commercial navigation.