wordpress custom rewrite rules

gistfile1.php

<?php
    function theme_rewrites( $wp_rewrite ) {
        $rules = array(
            'coordinates/([^/]+)/?$'       => 'index.php?pagename=coordinates&coords=$matches[1]',
        );

        $wp_rewrite->rules = array_merge( $rules, $wp_rewrite->rules );
    }

    add_action( 'generate_rewrite_rules', 'theme_rewrites' );