Convert NavParams to String

hello, i’m using typescript in my apps and i want to convert some data to string, my code is looks like :
// the variable
position_latitude:any
position_longitude:any
//my function
myRoad(){
this.platform.ready().then(()=>{
Geolocation.getCurrentPosition().then(pos => {
console.log('lat: ’ + pos.coords.latitude + ', lon: ’ + pos.coords.longitude);
this.position_latitude=pos.coords.latitude;
this.position_longitude=pos.coords.longitude;
});
LaunchNavigator.navigate([this.reponse.latitude, this.reponse.longitude],{
start : this.position_latitude + ‘’ + this.position_longitude
});
});
}