public Activity(GregorianCalendar startTime,GregorianCalendar endTime,GPSPoint point){
  this.startTime=startTime;
  this.endTime=endTime;
  this.location=point;
  this.startHour=startTime.get(GregorianCalendar.HOUR_OF_DAY);
  setDuration();
}

public Activity ( GregorianCalendar startTime , GregorianCalendar endTime , GPSPoint point ) { this . startTime = startTime ; this . endTime = endTime ; this . location = point ; this . startHour = startTime . get ( GregorianCalendar . HOUR_OF_DAY ) ; setDuration ( ) ; }
constructs an activity with following minimum parameters < p >
