latlng
$meta_query = array( array( 'key' => 'lat', 'compare' => 'EXISTS', ), array( 'key' => 'lng', 'compare' => 'EXISTS', ), );
$meta_query = array( array( 'key' => 'lat', 'compare' => 'EXISTS', ), array( 'key' => 'lng', 'compare' => 'EXISTS', ), );