Best, Martyn
 
bookmarks:

1) To use xtide at your location you need to obtain a harmonic constant
table (tcd extension) for your area. If you live in North America you
are in luck. Things further afield are no longer so easy (an example
where free data has unfortunately become non-free data). Further info
here: http://www.flaterco.com/xtide/harmonics.html

Note: I successfully managed to find data for England on Debians server,
named harmonics-dwf-20100529-nonfree.tcd which is suitable for me.