Can't get custom markers to work in Mapbox GL JS

Question

I've followed both the example at Mapbox site and this instruction on GitHub but can't get markers to show on my map:

http://codepen.io/znak/pen/waPPRj (using Mapbox style and sprites) http://codepen.io/znak/pen/PqOEyV (using custom style and sprites)

var center = [51.5, -0.1];

var map = new mapboxgl.Map({
    container: 'map',
    center: center,
    zoom: 8,
    style: 'https://www.mapbox.com/mapbox-gl-styles/styles/mapbox-streets-v7.json'
});

// Markers
map.on('style.load', function() {
    map.addSource("markers", {
        "type": "geojson",
        "data": {
            "type": "FeatureCollection",
            "features": [{
                "type": "Feature",
                "geometry": {
                    "type": "Point",
                    "coordinates": [51.48, -0.08]
                },
                "properties": {
                    "title": "Lorem",
                    "marker-symbol": "default_marker"
                }
            }, {
                "type": "Feature",
                "geometry": {
                    "type": "Point",
                    "coordinates": [51.52, -0.12]
                },
                "properties": {
                    "title": "Ipsum",
                    "marker-symbol": "secondary_marker"
                }
            }]
        }
    });

    map.addLayer({
        "id": "markers",
        "type": "symbol",
        "source": "markers",
        "layout": {
            "icon-image": "{marker-symbol}",
            "text-field": "{title}",
            "text-font": "Open Sans Semibold, Arial Unicode MS Bold",
            "text-offset": [0, 0.6],
            "text-anchor": "top"
        },
        "paint": {
            "text-size": 14
        }
    });
});

All styles, JSON and PNG files with markers seem to load properly. Any ideas?

Answer 1

The GeoJSON layer type of Mapbox GL JS follows the GeoJSON specification, which requires that coordinates be in longitude, latitude order. Your examples have them reversed. Flipping them shows the markers, which have the correct icons.

"geometry": {
    "type": "Point",
    "coordinates": [-0.12, 51.52]
}