Query multiple tables
Try this:

SELECT
  DAY(time_stamp) AS Day,
  COUNT(time_stamp) as Tot,
  SUM(CASE WHEN origin = 's' THEN 1 ELSE 0 END) as Syd,
  SUM(CASE WHEN origin = 'n' THEN 1 ELSE 0 END) as Norr
FROM (select time_stamp, 'n' as origin from ink_norr union all select time_stamp, 's' as origin from ink_syd) x
GROUP BY DAY(time_stamp) 
ORDER BY 1;