How to query custom post type one after another

Since version 4.0 is available 'type' option for 'orderby' argument in WP_Query.

Also, thanks to the more powerful ORDER BY in WordPress 4.0 you can control how posts of a post type are ordered.

Example (untested):

$q = new WP_Query(array(
    'post_type' => array('map','item'),
    'orderby'   => array(
       'type'   => 'DESC',
       'title'  => 'ASC'
    )
));