def load_fence(self, filename):
        '''load fence points from a file'''
        try:
            self.fenceloader.target_system = self.target_system
            self.fenceloader.target_component = self.target_component
            self.fenceloader.load(filename.strip('"'))
        except Exception as msg:
            print("Unable to load %s - %s" % (filename, msg))
            return
        print("Loaded %u geo-fence points from %s" % (self.fenceloader.count(), filename))
        self.send_fence()
load fence points from a file