Seamap.java - Planetiler Profile for Nautical Charts

Overview

This Java file implements a Planetiler profile that converts OpenStreetMap data directly into PMTiles vector tiles for nautical charts. It replaces the previous imposm3 + PostgreSQL workflow.

Features

1. Seamark Base Objects (seamark:* tags)

• Processes all seamark types: buoys, beacons, lights, landmarks, harbours, etc.
• Extracts comprehensive attributes:
  • osm_id, type, name, reference, function, category, shape
  • color, color_pattern (with semicolon → underscore conversion)
  • light (abbreviated format), light_color, light_sequence
  • topmark_color, topmark_shape (sanitized)
• Creates separate layers:
  • seamark_point - Point features
  • seamark_linestring - Line features
  • seamark_polygon - Polygon features with additional label points (PointOnSurface)

2. Derived Seamark Features

Maps standard OSM tags to seamark types:

OSM Tags	Seamark Type	Category	Geometries
route=ferry	ferry_route	-	linestring
waterway:sign=anchor	anchorage	-	point/line/polygon
power=cable + location=underwater	cable_submarine	power	linestring
man_made=pipeline + location=underwater	pipeline_submarine	substance	linestring
man_made=pier	mooring	pier	point/line/polygon
leisure=marina	harbour	marina	line/polygon
leisure=swimming_area|nature_reserve	restricted_area	leisure value	line/polygon
man_made=tower|windmill|gasometer	landmark	man_made	point
man_made=lighthouse	lighthouse	-	point (with full light attributes)

3. Land Layer

• Downloads and processes global land polygons from osmdata.openstreetmap.de
• Source: land-polygons-split-4326.zip (~600 MB)
• Projection: WGS84 (EPSG:4326)
• Automatic download on first run if not present
• Creates land layer with polygon features
• Attributes: None (simple land mask geometry)
• Buffer: 4 pixels for smooth rendering at tile boundaries

4. Light Sector Layer

Generates geometric representations of light sectors for navigational lights:

Light Geometries

• Arcs: Colored sector arcs showing the visible range of each light color
• Rays: Lines at sector boundaries marking the transitions between colors

Light Types

Type	Arc Radius	Ray Radius
light_major	0.7 NM (~1296m)	2.5 NM (~4630m)
light_minor	0.4 NM (~741m)	1.2 NM (~2222m)

Attributes

• osm_id (integer) - Reference to parent seamark
• type (string) - Parent seamark type (e.g., light_major, light_minor)
• subtype (string) - Geometry type: arc or ray
• color (string) - Light color for arcs (e.g., red, green, white)
• range (string) - Nominal range in nautical miles
• sector_start (integer) - Start bearing in degrees (0-360, for arcs only)
• sector_end (integer) - End bearing in degrees (0-360, for arcs only)

Source Tags

Processes seamark:light:N:* tags where N is the sector number:

• seamark:light:N:colour - Light color
• seamark:light:N:range - Nominal range
• seamark:light:N:sector_start - Sector start bearing
• seamark:light:N:sector_end - Sector end bearing

Example

For a lighthouse with red (0-120°) and green (120-240°) sectors:

• 2 arc features (one red, one green)
• 4 ray features (at 0°, 120°, 120°, 240°)

5. Places Layer

• Extracts natural=bay features
• Creates point geometry:
  • Points: direct geometry
  • Lines: centroid point
  • Polygons: point on surface
• Attributes: osm_id, type, subtype, name, reference

6. Default Values for IALA Maritime Buoyage System

Implements automatic defaults for standardized seamark types:

Cardinal Marks

• North: black_yellow horizontal, 2 cones up, black topmark
• East: black_yellow_black horizontal, 2 cones base together, black topmark
• South: yellow_black horizontal, 2 cones down, black topmark
• West: yellow_black_yellow horizontal, 2 cones point together, black topmark

Isolated Danger

• Color: red_black_red horizontal
• Topmark: 2 spheres, black

Safe Water

• Color: red_white vertical
• Topmark: sphere, red

Special Purpose

• Color: yellow

Generic Defaults

• All beacons: shape = buoyant (transformed from pile)
• All buoys: shape = pillar
• Colors with underscore: color_pattern = horizontal

5. Light Abbreviation

Replicates SQL seamark_light_abbr() function:

• Format: <character>(<group>).<COLORS>.<period>s<height>m<range>M
• Supports single and multi-light configurations
• Extracts max range per color
• Example: Fl(3).WRG.10s15m12M

Usage

Compile

javac -cp planetiler.jar Seamap.java

Run

java -Xmx4g -cp planetiler.jar:. Seamarks \
  --download \
  --area=austria \
  --output=seamarks.pmtiles \
  --force

Or for a local OSM file:

java -Xmx4g -cp planetiler.jar:. Seamarks \
  --osm-path=data/austria.osm.pbf \
  --output=seamarks.pmtiles \
  --force

Output Layers

Point/Line/Polygon features for all seamark objects

Attributes:

• osm_id (integer)
• type (string) - seamark type
• name (string)
• reference (string)
• function (string)
• category (string)
• shape (string)
• color (string)
• color_pattern (string)
• light (string) - abbreviated light characteristics
• light_color (string)
• light_sequence (string)
• topmark_color (string)
• topmark_shape (string)

Note: Polygon features also generate a corresponding point feature for labeling (using point on surface).

Build PMTiles file for the whole planet

This command takes about 1h on a strong hetzner machine (Ryzen 9 & 128 GB RAM)

java -Xmx20g   -XX:+UseParallelGC   -XX:ParallelGCThreads=4   -cp "/app/classes:/app/libs/*:/app/resources:."   Seamap.java   --download   --osm-url=https://planet.openstreetmap.org/pbf/planet-latest.osm.pbf   --maxzoom=14  --output=/data/seamap.pmtiles   --tmp=/data/tmp   --nodemap-type=array   --storage=mmap   --threads=20   --download-threads=10   --http-retries=3   --force

Demo Page (seamap.html)

The seamap.html file provides a complete MapLibre GL JS demonstration of the nautical chart visualization.

Data Sources

1. Base Map

• Provider: VersaTiles
• Style: Colorful style with desaturated colors (-30% saturation)
• Purpose: Base map with streets, labels, and general cartography

2. Seamark Vector Tiles

• Source: MapToolkit Data Connector
• Endpoint: https://dataconnector.maptoolkit.net/seamap/seamap/{z}/{x}/{y}.pbf
• Format: Vector tiles (PMTiles served via API)
• Max Zoom: 14
• Layers:
  • seamark - All nautical features (buoys, beacons, lights, etc.)
  • land - Land polygons for coastline
  • light - Light sector geometries (arcs and rays)

3. Seamark Sprites

• Source: MapToolkit Icons
• Endpoint: http://icons.maptoolkit.net/seamap
• Format: Sprite sheets with S-57 nautical symbols
• Purpose: Icon rendering for buoys, beacons, landmarks, etc.

4. Land Hillshading & Contours

• Provider: Mapterhorn
• Endpoint: https://tiles.mapterhorn.com/{z}/{x}/{y}.webp
• Encoding: Terrarium (RGB-encoded elevation)
• Max Zoom: 12
• Features:
  • Hillshading with 0.2 exaggeration
  • Dynamically generated contour lines
  • Contour intervals: 200m/1000m (z7), 100m/500m (z8-9), 50m/200m (z10), 20m/100m (z11), 10m/50m (z12)

5. Bathymetry (EMODnet)

• Source: MapToolkit Data Connector (EMODnet Bathymetry 2024)
• Endpoint: https://dataconnector.maptoolkit.net/seamap/emod/{z}/{x}/{y}.png
• Encoding: Terrarium (RGB-encoded depth values)
• Max Zoom: 11
• Coverage: European waters
• Features:
  • Bathymetric hillshading (0.2 exaggeration)
  • Dynamically generated depth contours
  • Contour lines at: 0m, 2m, 5m, 10m, 20m, 50m, 100m, 250m, 500m, 1000m, 2000m, 3000m, 4000m, 5000m
  • Depth area fills: 0-2m, 2-5m, 5-10m, 10-20m, 20-50m
  • Spot soundings (depth labels) with 32-pixel grid spacing

Technology Stack

• MapLibre GL JS: Open-source map rendering engine
• maplibre-contour (v0.2.8): Plugin for dynamic contour generation from DEM tiles
• VersaTiles Style: Base map styling library

Features Rendered

The demo visualizes:

• Bathymetry: Colored depth zones with contours and soundings
• Land: Coastline with terrain hillshading and elevation contours
• Seamarks: Buoys, beacons, lights with IALA colors and symbols
• Light Sectors: Colored arcs and rays showing navigational light coverage
• Navigation: Traffic separation schemes, fairways, anchorages
• Hazards: Rocks, wrecks with appropriate symbols
• Infrastructure: Cables, pipelines, platforms, landmarks

Create EMODnet Bathymetry

Download data

Download EMODnet bathymetry dataset (NetCDF format with elevation data for European waters)

wget https://erddap.emodnet.eu/erddap/files/bathymetry_dtm_2024/EMODnet_bathymetry_2024.nc

Download OSM land polygons (global coastline shapefile in WGS84)

wget https://osmdata.openstreetmap.de/download/land-polygons-complete-4326.zip
unzip land-polygons-complete-4326.zip

Process bathymetry data

1. Extract elevation layer from NetCDF and convert to GeoTIFF
   • Assigns WGS84 coordinate system (EPSG:4326)
   • Converts from NetCDF format to standard GeoTIFF raster

gdal_translate -a_srs EPSG:4326 NETCDF:"EMODnet_bathymetry_2024.nc":elevation bathymetry_elevation.tif

2. Rasterize land polygons to mask land areas
   • burn 0: Set land pixels to elevation 0 (sea level)
   • init nan: Initialize all pixels as NaN (no data)
   • tr: Target resolution ~0.00104° (~115m at equator, matching EMODnet resolution)
   • te: Extent covering Europe (-36°W to 43°E, 15°N to 90°N)
   • ot Float32: Output as 32-bit floating point for precise elevation values

gdal_rasterize -burn 0 -init nan -a_nodata nan -tr 0.001041666666666 0.001041666666666 -te -36 15 43 89.999999999933507 -ot Float32 -of GTiff -l land_polygons land-polygons-complete-4326/land_polygons.shp land0.tif

3. Merge land mask with bathymetry data
   • Overlays land0.tif (land=0) onto bathymetry_elevation.tif (ocean depths)
   • Preserves NaN values where no data exists in either source
   • Result: Combined raster with land at 0m and bathymetry for sea areas

gdalwarp -overwrite -ot Float32 -srcnodata "nan" -dstnodata "nan" -of GTiff land0.tif bathymetry_elevation.tif merged.tif

4. Fill small gaps in data using interpolation
   • md 5: Maximum distance of 5 pixels to search for valid values
   • Interpolates missing data (NaN) using surrounding valid pixels
   • Creates seamless bathymetry raster without gaps

gdal_fillnodata.py -md 5 merged.tif filled.tif

5. Create raster-dem tiles

This command takes about 10h on a strong Hetzner machine

rio rgbify -v -e terrarium --min-z 3 --max-z 11 -r -2 -j 4 --format webp filled_clipped.vrt emod.mbtiles
pmtiles convert emod.mbtiles emod.pmtiles