Signal K World Coastline Map

This repository is a plugin for the Signal K marine exchange Nodejs server. It adds a map of worldwide coastlines in zoom level 0-9. The format ist Mapbox MBTiles, a SQLite database file that contains all 350000 PNG tiles. Signal K stores all maps in the directory 'public/mapcache/'.

The repository itself does not include the map but depends on it. The map file is a separate NPM package with a size of 800MB.

How the Tiles are made

The tiles are rendered by an online service and packed into one single MBTiles file.

Tile design

Setup a map in Mapbox Studio. An approach to a simple map with just coastlines, countries and towns is in Coastline-Mapbox.zip. Start the live view (export to a friend). Switch to raster tiles and copy the tile URL. The tiles are PNGs with a size of 512x512.

Download

Open download.js and change the tile URL. Also change the zoom level you need. Create a directory "tiles/" where the tiles will be saved.

$ npm install
$ node download.js

The script first downloads the tiles and then moves them into a directory structure.

Complete tiles directory

You have directories with tiles. In the tiles/ directory add this metadata.json:

{
	"name": "World Coastline",
	"description": "The whole earth up to zoom level 9",
	"version": "1"
}

Convert into mbtiles format

All these small files are a pain on the hard drive. So let's convert them into one large database file.

Install a python tool for conversion to mbtiles format:

$ git clone https://github.com/mapbox/mbutil
$ ./mb-util --scheme=xyz --image_format=png   ../tiles/ coastline.mbtiles

The output is a file 'coastline.mbtiles'. If you want to test the tiles database, use mbtiles-server.

Install map in Signal K server

If you can not install the map using this plugin in the Signal K app store, do this:

Move this file to signalk-server-node/public/mapcache. After reboot you will see the map here: http://localhost:3000/signalk/v1/api/resources/charts

Done!