jku-ba-react/src/helpers/distance.js

  export const calcDistance = (path) => {
    let distance = 0;
    for(let i=0; i<path.length-1; i++) {
      if (path[i]===undefined | path[i+1]===undefined){
        continue
      }
      var radlat1 = Math.PI * path[i][0]/180;
      var radlat2 = Math.PI * path[i+1][0]/180;
      var theta = path[i][1]-path[i+1][1];
      var radtheta = Math.PI * theta/180;
      var d = Math.sin(radlat1) * Math.sin(radlat2) + Math.cos(radlat1) * Math.cos(radlat2) * Math.cos(radtheta);
      if (d > 1) {
        d = 1;
      }
      distance += Math.acos(d) * 180/Math.PI * 60 * 1.1515 * 1.609344;
    }
    return distance
  }