Updating Custom Post Meta Issue 1

function heymap_post_class_meta_box($post) {

	echo '<script type="text/javascript" src="https://maps.google.com/maps/api/js?sensor=false"></script>'. "\n";
	echo '<script type="text/javascript" src="'.heyKARTE_PLUGIN_URL.'/hey-map.js"></script>' . "\n";
	if(is_numeric(get_post_meta($post->ID, 'heymap-position-lon', true )) && is_numeric(get_post_meta($post->ID, 'heymap-position-lat', true ))) $markerSet = true;
	wp_nonce_field( basename( __FILE__ ), 'heymap_post_class_nonce' ); ?>

	<p>
	<div id="heymap" style="height:300px;"></div>
	Aktuelle Markerposition (Länge, Breite): <strong id="heymap_show_current_position"><?php if($markerSet) echo get_post_meta($post->ID, 'heymap-position-lon', true ).', '.get_post_meta($post->ID, 'heymap-position-lat', true ); else echo 'keine Position gesetzt'; ?></strong><br />
		<input type="hidden" name="heymap-position-lon" id="heymap-position-lon" value="<?php echo get_post_meta($post->ID, 'heymap-position-lon', true ); ?>" />
		<input type="hidden" name="heymap-position-lat" id="heymap-position-lat" value="<?php echo get_post_meta($post->ID, 'heymap-position-lat', true ); ?>" />
	</p>
<?php
	echo '<script type="text/javascript">if(document.getElementById("heymap")) heymap_init('.get_option('heymap-lon-center').','.get_option('heymap-lat-center').','.get_option('heymap-zoom').','.get_option('heymap-minzoom').',"'.get_option('heymap-type').'",'.get_option('heymap-lat-northeast').','.get_option('heymap-lon-northeast').','.get_option('heymap-lat-southwest').','.get_option('heymap-lon-southwest').'); </script>';
	if($markerSet) echo '<script type="text/javascript"> placeCurrentMarker(map,'.get_post_meta($post->ID, 'heymap-position-lon', true ).','.get_post_meta($post->ID, 'heymap-position-lat', true ).'); </script>';

}