Signal K Charts Provider Simple

A lightweight Signal K server plugin for managing local nautical charts, written in strict TypeScript. Supports MBTiles, S-57 ENC, BSB raster, and world basemaps with automatic conversion via Docker- or Podman-managed containers.

Features

• Local Chart Management: MBTiles (raster and vector), with folder organization and enable/disable toggles
• Download Manager: Built-in download queue with progress tracking and ZIP extraction
• Chart Catalog: Browse and download charts from chartcatalogs.github.io with automatic update notifications
• S-57 ENC Conversion: Convert IENC/ENC charts to vector MBTiles with full S-52 symbology in Freeboard-SK
• BSB Raster Conversion: Convert BSB/KAP raster charts and Pilot Charts to raster MBTiles
• World Basemaps: GSHHG and OSM coastline basemaps for offline use
• Custom Upload: Upload your own ZIP files containing S-57 ENC or BSB charts for conversion
• Modern Web UI: Material Design 3 interface with drag-and-drop
• Dual API Support: Compatible with Signal K v1 and v2 API

Installation

From Signal K Appstore

1. Open your Signal K server admin interface
2. Navigate to Appstore
3. Search for "Charts Provider Simple"
4. Click Install

Manual Installation

cd ~/.signalk
npm install signalk-charts-provider-simple

Configuration

1. Navigate to Server → Plugin Config → Charts Provider Simple
2. Set your chart directory path (defaults to ~/.signalk/charts-simple)
3. (Optional) Pick a CPU budget for chart conversion — see CPU budget below
4. Enable the plugin
5. Restart Signal K server (first-time install only — later config changes hot-apply on Save without a full restart)

CPU budget for chart conversion

Chart conversion (S-57 ENC, BSB raster, basemaps) is the only CPU-heavy thing this plugin does. The CPU budget dropdown lets you decide how greedy that work is allowed to be:

| Setting | What happens during a conversion | When to pick it | |---|---|---| | single-core | One job at a time, one thread; each ogr2ogr runs sequentially | Multi-tenant Pi (Signal K + Grafana + Node-RED + …) where keeping the rest of the box responsive matters more than conversion speed | | half (default) | cpus/2 concurrent jobs, each tippecanoe gets cpus / max-jobs threads (typically ~2), ogr2ogr parallelizes to the same per-job ceiling | Balanced — leaves half the box for everything else. Matches the behaviour of plugin versions before 1.10 | | all | One full-throttle job using every core in both the GDAL export and tippecanoe stages; multi-bundle uploads queue serially | Dedicated chart-prep box, or when you just want a NOAA bundle to finish as fast as possible |

The setting hot-applies — change it in the plugin config and Signal K will restart the plugin automatically; no server restart needed. In-flight conversions keep their already-spawned threads; the next conversion picks up the new budget.

Usage

Web Interface

Access the plugin's web interface through your Signal K server:

http://[your-server]:3000/plugins/signalk-charts-provider-simple/

The interface provides four tabs:

1. Manage Charts:

   • View all charts with metadata (name, bounds, zoom levels, size)
   • Enable/disable, organize into folders, upload, delete, rename
   • S-57 charts shown with ENC badge
   • Converting charts shown with progress indicator

2. Download from URL:

   • Download charts directly from any URL
   • Supports .mbtiles and .zip archives
   • Download queue with progress tracking

3. Convert:

   • Upload ZIP files containing S-57 ENC (.000) or BSB raster (.kap) charts
   • Drag-and-drop or click to select files
   • Configurable zoom levels for S-57 conversion
   • Live conversion progress with log viewer

4. Chart Catalog:

   • Dynamic catalog from chartcatalogs.github.io
   • One-click download for MBTiles charts (NOAA)
   • Download & convert for S-57 ENC, BSB raster, Pilot Charts, and basemaps
   • Automatic update notifications (Signal K delta + tab badge)
   • Category filtering (MBTiles / RNC / IENC / General)

Supported Formats

| Format | Source | Conversion | Output | |--------|--------|-----------|--------| | MBTiles | Direct download | None needed | Raster or vector tiles | | S-57 ENC (.000) | IENC catalogs, custom upload | GDAL + tippecanoe (containerized) | Vector MBTiles with S-52 styling | | BSB Raster (.kap) | RNC catalogs, custom upload | GDAL (containerized) | Raster MBTiles (PNG) | | Pilot Charts (.kap in .tar.xz) | Pilot catalog | GDAL (containerized) | Raster MBTiles (PNG) | | GSHHG Basemap | General catalog | GDAL (containerized) | Raster MBTiles (PNG) | | OSM Basemap | General catalog | GDAL (containerized) | Raster MBTiles (PNG) |

Compatible Chart Plotters

• Freeboard SK — full S-52 symbology for S-57 vector charts
• OpenCPN

Requirements

• Node.js >= 22.5 — uses the built-in node:sqlite module, no native compilation needed
• Not supported on Cerbo GX — Venus OS ships Node.js 20, which lacks the node:sqlite module. Use v1.6.x if you need Cerbo support.

Optional: container runtime (for chart conversion)

To convert S-57 ENC, BSB raster, Pilot Charts, or basemaps, the plugin needs a Docker- or Podman-compatible API socket. Both engines work the same way; pick whichever is easier on your host.

The plugin uses standard images that are pulled automatically on first use:

• ghcr.io/osgeo/gdal:alpine-small-latest — GDAL for format conversion
• ghcr.io/dirkwa/signalk-charts-provider-simple/tippecanoe — tippecanoe for vector tile generation (multi-arch: amd64 + arm64)

Bare-metal install (Signal K running directly on the host):

# Debian / Ubuntu / Raspberry Pi OS
sudo apt install podman
systemctl --user enable --now podman.socket

# Fedora / RHEL
sudo dnf install podman
systemctl --user enable --now podman.socket

Signal K running in Docker? See docs/running-in-docker.md for the docker-compose snippet.

Conversion concurrency is configurable — see the CPU budget section. MBTiles charts (display only, no conversion) work without any container runtime.

Known install warnings

Signal K's appstore installs plugins with --ignore-scripts, so any optional native addons in the dependency tree won't compile. CI flags one such case for this plugin:

Optional native addons found: cpu-features. App Store uses --ignore-scripts so these will not be compiled.

This is harmless. cpu-features is a transitive optional dependency of ssh2, pulled in by dockerode. The plugin only ever talks to a local Docker/Podman Unix socket, so the SSH transport (and its native crypto accelerator) is never used. The warning is informational; the plugin runs fully without the addon.

Legal Notice

Chart Metadata Editing

This plugin includes a feature to edit chart metadata (chart names) in MBTiles files. This feature is intended for personal use only.

Important:

• The Signal K community is not responsible for any illegal use of this feature
• Modified charts are automatically marked with "USER MODIFIED - DO NOT DISTRIBUTE - PERSONAL USE ONLY" in the description field
• Do not distribute modified charts - this may violate copyright laws
• Use this feature responsibly and only for organizing your personal chart library

Acknowledgments

Inspired by Signal K Charts Plugin by Mikko Vesikkala.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Support

For issues and feature requests:

• GitHub Issues: https://github.com/dirkwa/signalk-charts-provider-simple/issues