Error _.K {lat: ƒ, lng: ƒ} or setpostion of latlong not number

Ionic Framework ionic-v3
1

the lat and long is changable as realtime tracking from data , i use get http from url, and i use interval observoable to reload but i fail to add marker to map and make it move .

error

fetchplane() {
    return new Promise(resolve => {
      this.http.get<dornelocation>('http://api.open-notify.org/iss-now.json'
      ).subscribe(data=>{
       this.droneMarker(data);
      }, err => { console.log(err); });
    });
  }
loadMap()
  {  
    var latlong = new google.maps.LatLng(2.909047 , 101.654669);
      var loptions = {
        center: latlong,
        zoom:1,
        mapTypeId: google.maps.MapTypeId.ROADMAP
      }
      this.map= new google.maps.Map(this.mapElement.nativeElement, loptions);
      this.droneMarker(latlong);
  }
droneMarker(data) {
      var Newlat = data.iss_position.latitude;
      var nlat = +Newlat;
      var Newlng = data.iss_position.longitude;
      var nlng = +Newlng;
    var latlong = new google.maps.LatLng([nlat, nlng]);
      console.log(latlong);
      return new google.maps.Marker({
        position: latlong,
        map: this.map,
        icon: {
          url: 'assets/markers/drone_location.png',
          scaledSize: new google.maps.Size(80, 80),
        }});}
2 
droneMarker(data) {
    var Newlat = data.iss_position.latitude;
      var Newlng = data.iss_position.longitude;
    var latlong = {Newlat, Newlng};
      console.log(latlong);
    const marker =new google.maps.Marker({
        position: {
          lat: parseFloat(data.iss_position.latitude),
          lng: parseFloat(data.iss_position.longitude)
        },
        map: this.map,
        icon: {
          url: 'assets/markers/drone_location.png',
          scaledSize: new google.maps.Size(80, 80),
        }
      });
     
  }