  type: 'FeatureCollection',
                        features: []
                    }
                }
            );

            map.addSource('tracks', {
                    type: 'geojson',
                    data: {
                        type: 'FeatureCollection',
                        features: geojsonfeatures
                    }
                }
            );

            map.addLayer({
                id: 'tracks-layer',
                type: 'line',
                source: 'tracks',
   