On Thursday, March 21, 2019 at 7:39:23 AM UTC-4, V. Kelly Bellis wrote: > > > Why in the world would I ever want to have anything but a current version > of xtide? And moreover, old harmonics data, i.e., circa 20100529 - why > would I want that added liability? A better question would be: why isn't > forecast able to integrate a modern version of tide? >
ah, but the forecast extension DOES work with ANY version of xtide. why would you want to install the latest xtide, when the one from 2010 produces exactly the same results? only the harmonics need to be updated, and for some locations those don't even matter that much when someone asks "does forecast work with the latest version of xtide?" it is rather handy to have 2 (or 5 or 10) different versions of xtide or its harmonics installed at once so that i can answer accurately. > From your remarks, it sounds like you don't have v2.15.2 working yet with > forecast and that you've retained v2.13 (or earlier) explicitly for tide's > integration into forecast. Or have I misread something? > apparently you misread > I'm not a programmer, but it seems that forecast.py (and maybe other > related bits of python) is predicated on the placement of xtide in a > particular environment instilled from a Debian-style package installation > without any provision for building xtide from source files. All of this is > still pretty alien to me, but in so far as I'm able, I'm interested in > helping find a solution to this problem as I love that local tide > predictions can be presented alongside local weather forecasts. > the default installation assumes that tide is located at /usr/bin/tide this can be changed with the `prog` option. as long as the thing referred to by `prog` produces output in the format produced by the 'tide' program (which is unchanged since 1999 or so), then everything works. so maybe some examples will help: here is output from tide version 2.11 for boston harbor using two different harmonics files. the first harmonics file is from 2010, the second one is from 2018. the differences in tide magnitude and timing are minimal. if you do the same test for boston light, there is more variation, but still pretty small. tide -l'Boston, Boston Harbor' -b'2019-03-21 00:00' -e'2019-03-22 00:00' Indexing /usr/share/xtide/harmonics-initial.tcd... Indexing /usr/share/xtide/harmonics-dwf-20100529-free.tcd... Boston, Boston Harbor, Massachusetts 42.3550° N, 71.0533° W 2019-03-21 5:58 AM EDT -1.53 feet Low Tide 2019-03-21 6:46 AM EDT Sunrise 2019-03-21 7:26 AM EDT Moonset 2019-03-21 12:13 PM EDT 11.82 feet High Tide 2019-03-21 6:26 PM EDT -1.72 feet Low Tide 2019-03-21 6:57 PM EDT Sunset 2019-03-21 7:50 PM EDT Moonrise HFILE_PATH=/opt/harmonics/harmonics-dwf-20181227/harmonics-dwf-20181227-free.tcd tide -l'Boston, Boston Harbor' -b'2019-03-21 00:00' -e'2019-03-22 00:00' Indexing /opt/harmonics/harmonics-dwf-20181227/harmonics-dwf-20181227-free.tcd... Boston, Boston Harbor, Massachusetts 42.3539° N, 71.0503° W 2019-03-21 5:58 AM EDT -1.52 feet Low Tide 2019-03-21 6:46 AM EDT Sunrise 2019-03-21 7:25 AM EDT Moonset 2019-03-21 12:13 PM EDT 11.83 feet High Tide 2019-03-21 6:26 PM EDT -1.71 feet Low Tide 2019-03-21 6:57 PM EDT Sunset 2019-03-21 7:50 PM EDT Moonrise now lets look at ellsworth maine: tide -l'Ellsworth' -b'2019-03-21 00:00' -e'2019-03-22 00:00' Indexing /usr/share/xtide/harmonics-initial.tcd... Indexing /usr/share/xtide/harmonics-dwf-20100529-free.tcd... Ellsworth, Union River, Blue Hill Bay, Maine 44.5350° N, 68.4217° W 2019-03-21 5:49 AM EDT -1.50 feet Low Tide 2019-03-21 6:35 AM EDT Sunrise 2019-03-21 7:15 AM EDT Moonset 2019-03-21 11:59 AM EDT 13.23 feet High Tide 2019-03-21 6:15 PM EDT -1.72 feet Low Tide 2019-03-21 6:47 PM EDT Sunset 2019-03-21 7:39 PM EDT Moonrise HFILE_PATH=/opt/harmonics/harmonics-dwf-20181227/harmonics-dwf-20181227-free.tcd tide -l'Ellsworth' -b'2019-03-21 00:00' -e'2019-03-22 00:00' Indexing /opt/harmonics/harmonics-dwf-20181227/harmonics-dwf-20181227-free.tcd... Ellsworth, Union River, Blue Hill Bay, Maine 44.5350° N, 68.4217° W 2019-03-21 5:48 AM EDT -1.29 feet Low Tide 2019-03-21 6:35 AM EDT Sunrise 2019-03-21 7:15 AM EDT Moonset 2019-03-21 12:00 PM EDT 13.01 feet High Tide 2019-03-21 6:16 PM EDT -1.63 feet Low Tide 2019-03-21 6:47 PM EDT Sunset 2019-03-21 7:39 PM EDT Moonrise interesting! there is more variation here, probably because of the geography - the ellsworth tidal area is considerably different from boston harbor. but the differences are still pretty small (unless you're on a boat and you really need that additional 1.-2.5" of draft or that 1 minute time shift). of course, if you run your own tide station you could figure out whether the xtide harmonics are actually accurate for your location - they might be inter-station approximations. so it might not be worth sweating the 1.-2.5" difference unless/until you get some data that show the 1.-2.5" is accurate. -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to weewx-user+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
