Comparison between the 
correspondig maxima, 
in year, Stockholm tide gauge
=============================
ObsPer     DerPer
-----------------------------
161.4      161.4
141.2      141.3
 ----       94.2
 62.8       62.8
 40.4       40.4
 29.7       29.7
 ----       20.5
 18.2       18.5
 16.6       16.1
 15.1       ----
 14.3       14.5
 11.8       11.8
  9.0        9.0
  8.5        8.5
  6.6        6.8
  6.2        6.1
  4.8        4.8
  4.2        4.1
  3.8        3.8
  3.2        3.2
  1.3        1.3