GeoJSON Map Fit Mercator

Given a set of GeoJSON features finds the optimal bearing, zoom and center point for fitting all features in a Mapbox GL or MapLibre GL viewport. The optimal viewport is calculated by determining the optimal bearing and zoom level to present a minimum bounding rectangle (MBR) of all the given GeoJSON features. This can allow you to render more detailed, better fitting maps than the default bounding box behaviour which only describes a x/y aligned minimum bounding rectangle.

Preview

Usage

mapFitFeatures returns an object describing the optimal center point (center), bearing (bearing) and zoom level (zoom) to display the given GeoJSON features in a given resolution map.

Mapping Library MapLibre GL JS Mapbox GL JS

    
import { mapFitFeatures } from 'geojson-map-fit-mercator';
import maplibregl from 'maplibre-gl';
import mapData from './map-data.json' with { type: 'json' }; // Load GeoJSON data

const { bearing, center, zoom } = mapFitFeatures(
  mapData,
  [600, 300]
);

const map = new new maplibregl.Map({
  container: 'map', // container ID for a 600px by 400px element
  style: 'https://demotiles.maplibre.org/style.json',
  center: center, // starting position [lng, lat]
  zoom: zoom, // starting zoom
  bearing: bearing // starting bearing
});

...

    
import { mapFitFeatures } from 'geojson-map-fit-mercator';
import mapboxgl from 'mapbox-gl';
import mapData from './map-data.json' with { type: 'json' }; // Load GeoJSON data

const { bearing, center, zoom } = mapFitFeatures(
  mapData,
  [600, 300]
);

const map = new new mapboxgl.Map({
  container: 'map', // container ID for a 600px by 400px element
  center: center, // starting position [lng, lat]
  zoom: zoom, // starting zoom
  bearing: bearing // starting bearing
});

...

Padding

You can add padding around the features in the viewport by passing an object to the padding option of mapFitFeatures. This padding object is identical to the Mapbox GL JS paddingOptions object and MapLibre GL JS paddingOptions object.

  mapFitFeatures(
    mapData,
    [600, 300],
    {
      padding: {
        top: 50,
        bottom: 50,
        left: 100,
        right: 100
      }
    }
  );

Bearing Preference

You can specify a preferred bearing for the map by passing the bearing option to mapFitFeatures. The preferred bearing will be used to pick the preferred orientation of the map to fit the minimum bounding rectangle of the features. This defaults to 0 which prefers to point the map in a northerly bearing.

  mapFitFeatures(
    mapData,
    [600, 300],
    {
      preferredBearing: 180 // Prefer to point the map south
    }
  );

Additional Features and Documentation

A full set of options and parameter descriptions for mapFitFeatures such as tile-size and zoom preferences are described in the API section of the Readme.