New Grib Presentation

[rgleason]

Uwe, Just register on Tracker and VOTE please
OpenCPN::Tracker Register new user

[HUR450502]

Originally Posted by rgleason

Uwe, Just register on Tracker and VOTE please
OpenCPN::Tracker Register new user

..... done .....

[rgleason]

HUR450502 in post above
http://www.cruisersforum.com/forums/...ml#post1451825

Advises using AirMail and requesting a 16 day grib

The last field simply is the date and hour (UTC) when the request was created. Format is YYYYMMDDHH. What Saildocs does with it, I do not know ....

...from day 8. on, there are only entries every 6 hours, which makes sense, as the prediction is by no means close to precise by then...

In HUR's post above, I am not sure what the listing of Airmail output is doing or for.

[rgleason]

I've been trying to learn grib formatting by email of requests.
I find the following works fine, without the date at the end, why complicate things?
To: query-grib@saildocs.com
Subject: gribauto
Body:

GFS:42N,38N,070W,76W|0.5,0.5|6,9,12,15,18,24,30,36,42,48,54,60,66,72,84,96,108,120,132,144,156,168,180,192,204,216,228,240,252,264,276,288,300,312,324,336,348,360,372,384|WIND|6.0,079

Area: 42N to 38N and 070W to 076W
Resolution: Starts at 0.5 x 0.5 and changes to 2 x 2 at 192 hours or 8 days
Intervals:
6 - 18 hours 3 hr intervals 0.5 x 0.5
18 - 84 hours 6 hr intervals 0.5 x 0.5
84 - 192 hours 12 hr intervals 0.5 x 0.5
192 - 384 hours 12 hr intervals 2.0 x 2.0

It would be nice to shorten the request and reduce size by adjusting the intervals and frequency, but that would be the next step.

The file size is 14kb. Needs to be somewhat smaller I think for over SSB which can be achieved several ways.

[rgleason]

WALKING GRIBS (Stepped or Moving Gribs)
==============
GFS:42N,38N,070W,76W|0.5,0.5|6,9,12,15,18,24,30,36 ,42,48,54,60,66,72,84,96,108,120,132,144,156,168,1 80,192,204,216,228,240,252,264,276,288,300,312,324 ,336,348,360,372,384|WIND|6.0,079
(First longhand version that returned the expected grib)
=======
GFS:42N,38N,070W,076W|0.5,0.5|6,9,12,15,18..84,96. .384|WIND|6.0,079
(same as above, just a shorter line)
To: query-grib@saildocs.com
Subject: gribauto
Body:
Area: 42N to 38N and 070W to 076W
Resolution: Starts at 0.5 x 0.5 and changes to 2 x 2 at 192 hours or 8 days
Intervals:
6 - 18 hours 3 hr intervals 0.5 x 0.5
18 - 84 hours 6 hr intervals 0.5 x 0.5
84 - 192 hours 12 hr intervals 0.5 x 0.5
192 - 384 hours 12 hr intervals 2.0 x 2.0

It would be nice to shorten the request and reduce size by adjusting the intervals and frequency, but that would be the next step.

GFS20140129205703845.grb
File size is 14kb. 16 days.
Needs to be somewhat smaller I think for over SSB which can be achieved several ways.

======
GFS:42N,38N,070W,076W|0.5,0.5|6,9..18,24,30..84,96 ,108..192,216,240..384|WIND|6.0,079
(Changed hours 192-384 to 24 hr interval)

6 - 18 hours 3 hr intervals 0.5 x 0.5
18 - 84 hours 6 hr intervals 0.5 x 0.5 (84 hrs = 7 days)
84 - 192 hours 12 hr intervals 0.5 x 0.5 (192 hrs = 8 days)
192 - 384 hours 24 hr intervals 2.0 x 2.0 (384 hrs = 16 days)

GFS20140129210203856.grb
File is 13kb, 16 days

======
GFS:42N,38N,070W,076W|0.5,0.5|6,9..18,24..84,96,10 8..192|WIND|6.0,079
(Dropped 192 - 384 hours)

6 - 18 hours 3 hr intervals 0.5 x 0.5
18 - 84 hours 6 hr intervals 0.5 x 0.5 (84 hrs = 7 days)
84 - 192 hours 12 hr intervals 0.5 x 0.5 (192 hrs = 8 days)

GFS20140129210203856.grb
File is 12kb, 8 days

=====
Note:
There is not much difference in size between these gribs. To get them smaller, it would be helpful if we could specify resolutions more precisely
EG
To 24 hours 0.5 x 0.5
To 36 hours 1.0 x 1.0
after that 2.0 x 2.0
It might make the files smaller. They are already very small but with SSB every kilobyte counts.

The files are attached for messing with. Take thee Doc off.

[rgleason]

In looking for more information about grib resolution a search turned up these links:
GFS Products
Inventory of GFS Files on NOMADS
NOMADS-NOAA Operational Model Archive and Distribution System

This is all very basic grib data I think
It appears that the resolutions NOAA uses are
0.5 x 0.5
1.0 x 1.0
2.5 x 2.5
Why does the plugin dropdown show 2.0 x 2.0 then? Is this a saildocs thing? -GFS is 2.5 why would saildocs change that?

I've found an excellent Grib help site on SAILGRIB.com I use the SailgribWR app. Their User Guide has Section "2. Specify your Grib files"

You can specify your grib request in the [Request Settings] menu. The following parameters can be adjusted:

• model: GFS, WW3 or COAMPS with SailDocs
  • GFS: The most often used. Produced by the NOAA. This is a global model that covers the entire globe. Data are available on a 0.5° x 0.5° grid every 3 hours out to 192 hours, and then on a 2.5-deg grid out to 384 hours (16 days). Data are calculated for 00:00, 06:00, 12:00,18:00 and are available by HH+05:00. Available data are winf, pressure, precipitation, total cloud cover, air temperature, significant wave height and cape.
  • WW3: This is NOAA's WaveWatch III wave model. The model is global but covers only open seas; the Mediterranean sea is not covered. Data are available on a 1° x 1.25° grid (lat x lon), forecasts every 3 hours out to 180 hours. Data are calculated for 00:00, 06:00, 12:00,18:00 and are available by HH+06:00. Available and default parameters are wind, significant wave height, mean wave direction and period.
  • COAMPS: This is a meso-scale regional model provided by the US Navy. Data are available for four regions: Europe and Mediterranean Sea, eastern Pacific, west Atlantic, and Caribbean/Central America. Forecast data are available on a 0.2° x 0.2° grid at 6-hour intervals out to 72 hours for Europe and Mediterranean Sea plus West-Atlantic and 48 hours for the other 2 regions. Available and default parameters are wind and pressure.

The available regions are:

- Europe and Mediterranean Sea:29n,66n,15w,45e
- East-Pacific: 29n,60n,160w,114w
- West-Altantic: 20n,55n,093w,055w
- Central-America and Caribbean: 00n,32n,120w,060w

[rgleason]

Continuing the "Walking" Grib study

The "Walking" or "Moving" GRIB requests found to work with Saildocs.com Grib server are:
Post #306 http://www.cruisersforum.com/forums/...ml#post1453674

GFS:42N,38N,070W,76W|0.5,0.5|6,9,12,15,18,24,30,36 ,42,48,54,60,66,72,84,96,108,120,132,144,156,168,1 80,192,204,216,228,240,252,264,276,288,300,312,324 ,336,348,360,372,384|WIND|6.0,079
-Longhand out to 384 hours or 16 days. 14kb file

GFS:42N,38N,070W,076W|0.5,0.5|6,9..18,24..84,96,10 8..192|WIND|6.0,079
-Shorthand out to 192 hours or 8 days. 12kb

GFS:42N,38N,070W,076W|1,1|6,9..18,24..84,96,108..1 92|WIND|6.0,079
- Change to 1x1 resolution 8 days, 6.2 kb

GFS:42N,38N,070W,076W|0.5,0.5|6,9..18,24..84,96,10 8..120|WIND|6.0,079
- Change back to 0.5x0.5 resolution and change to 5 days, 9 kb

=====

I think we would like the following:
0.5 x 0.5 resolution to 4 days (96h) with 6h interval up to 2 days (24h), and 12h interval up to 4 days (96h)
1x1 resolution to 8 days (192h) with 12h interval.
2x2 resolution to 16 days (384h) with 24h interval.

There does not seem to be the means to do that in one request. We could ask for two gribs and combine them.
GFS:42N,38N,070W,076W|0.5,0.5|6,9..18,24..84,96|WI ND|6.0,079
7.7 kb GFS20140130154302782.grb

GFS:42N,38N,070W,076W|1,1|108,120,132,144..192|WIN D|6.0,079
2.0 kb GFS20140130154402785.grb

GFS:42N,38N,070W,076W|2,2|216,240..384|WIND|6.0,07 9
1.48 kb GFS20140130154502788.grb
See attached.

How long do you think it would take to download these smaller 6.2 kb and 8.5 kb files via SSB + Pactor?

Now I'll attempt to merge or concatenated using the DOS command line.

From the DOS cmd line the command needed is: copy file1+file2 appendedfile /b (for binary files) So:
copy GFS20140130154302782.grb+GFS20140130154402785.grb+GFS20140130154502788.grb 20140130-384h.grb /b
This does not work properly, a file 1 kb in size is created with missing frames. See attached.

Then was trying a two stage merge of grib files but that does not work either.
copy GFS20140130154302782.grb+GFS20140130154402785.grb temp.grb /b
copy temp.grb+GFS20140130154502788.grb 20140130-384h.grb /b
See attached temp.grb.

Perhaps the Opencpn Grib_pi plugin should offer this Walking Grib and Regular Grib MERGE utility.

If anyone has some easy suggestions for MERGING GRIBs it would be appreciated.
from searches
http://www.dtcenter.org/met/users/su...ygb/copygb.txt
http://stackoverflow.com/questions/60244/is-there-replacement-for-cat-on-windows
concatenating grib (era40) files
Re: can ncl merge two nc files into one nc fil from David Brown on 2009-09-14 (ncl-talk 2009 archive)
Climate Prediction Center - wgrib2: -for see bottom for grib2

[Gilletarom]

hello Ptizef,

With OpenCPN 3.3.1328 and Grib V2.2.

I asked a loaded grib file Saildocs. In my application, I just checked in order to have the waves.

It opens well. But when I view the waves, there is a problem with the arrows displayed.
For example, (we must look at where is the mouse) can have a display that says the wave is 3 meters and announced the direction is 90 °. But the arrow goes from right to left.
- Either there should be a direction 270 °.
- Let the arrow should go from left to right.

I compared with zyGrib. Unless I am mistaken, for example 28N and 40W, wave direction is announced at 83 °. And has the same information with OpenCPN.

It seems to me that the arrow of the wave at that point the wrong in the right direction. (The "direction" is good but not "sense")

Sorry, I cannot send the grib file because it is too big (even I zip it)

But, I have a doubt ... Is the same that with wind arrow ???? And then no problem ?

[Gilletarom]

Hello Ptizef.

In post # 308, I thought I saw a bug that does not exist. As for arrows wind the wind is said whence, for waves, we also say where they come from.
Thus, a wave from east to west goes to 270 °, but it comes from 90 °. And meteorology, we chose to tell where the phenomena are rather to say than where they are going.

Sorry for telling stupidity.

Gilletarom.

[Ptizef]

Originally Posted by Gilletarom

Hello Ptizef.

And meteorology, we chose to tell where the phenomena are rather to say than where they are going.

Gilletarom.

Yes, except For currents for which we say where it bring the boat to ....

That the rules I ever seen and a sailor instructor should teach to his students

JP

[Gilletarom]

Hello Ptizef ,

I argued quite seriously about plugin GRIB V2.2, my web page , web page which will be in the next version of the tutorial opencpn.shoreline.fr .

Although I am able to preposterous as that of post # 308 idea, I hope it will not be placed in the web page.
That said, it is a topic that has posed a problem for me , is that of the " Mode d'affichage " in the preferences accessed by clicking the "Heart" button.

After various attempts to translate the language file and the corresponding web page of the site opencpn.org , it was necessary that I admit that I could not understand the functioning of this part of the plugin.

So I conducted a battery of tests from grib files loaded in Saildocs ( zygrib but those would have given the same result ) . And .... there was light ....

This part of the plugin works fine BUT , in my opinion , we should not take for granted the texts of two items of the language file in English nor the explanations provided by the opencpn.org site.

I thought about an essay in French , of these items. Here is a direct link to my explanations are in the web page.
OpenCPN et l'affichage des fichiers mto (GRIB)

Attention : Many screen copy in this page and so, be shure you have a good internet.

And then down , much lower on the page, you will find a temporary copy of the web page of the site opencpn.org and down in this print , you will find the place where, in my view , the explanations are inadequate. I have inserted some " Ndlr " .

It also joined the French language file that I currently proposed (for test).

For you to give me your opinion .


Now that I've solved this problem, I will address myself to the "Afficher" the same preferences. If I have problems, I will discuss later. In any case, for sure, this part "Affichage", the language file will still be changed.

B.R. Gilletarom.

[kiltym]

I apologize if some of this is covered in this thread, but I am on a poor connection and can't get through all the pages to research.

I have O 3.3.1328 running the GRIB 2.2 Plugin.

I had a couple of questions:

1) I make a request and get a Grib containing Wave Period (WVPER) from saildocs (my own request, not through the Grib tool). The wave period does not seem to be shown in the new plugin when wave data is shown. I see height and direction, but why no period? This is almost as important as the height. Seems it should be displayed, as well as an option on the Grib Request function.

2) I like to put my mouse in a specific location on the overlaid grib, and then use the up and down arrows to move through time so I can watch the difference and move back and forth among the dates/times easily. What I find happening though is that with the cursor in a specific location, when I move the date and time with the arrow keys (that combo box has focus), the data in the boxes (wind, wave, etc), does not update. I need to wiggle the mouse a bit to get it to update. The data overlaid in the chart changes as I would expect, but the values are not updated. To reproduce, click on the date/time in the Grib window, then move your mouse to a location that has grib data, not use the arrow keys to change the date/time.

Thanks for your help, and thanks for working on the changes.

PS. I am on Windows 7 if that make a difference.

[kiltym]

I have another issue/question also.

I just got a Grib file (again using Saildocs), with rain (APCP).

I do see the values displayed, but I don't believe them. I have it showing in inches, and I have values as high as 23 inches.

I suspect its an issue of the conversion from mm to inches, as the mm readings look normal.

[kiltym]

I have another one.

I am comparing wind speed (in knots), from V2.2 to V1.4.

The values I get in 2.2 are all 1 knot higher then what I see in 1.4.

I have no idea which is correct, but if I see 11kts in 2.2 for a specific location/time, I see 10kts using 1.4.

Someone ought to see which is correct though, 2.2 or 1.4, and make sure the update 2.2 is correct.

Thanks!

[bdbcat]

kiltym....

Thanks for the reports. If you have the time, please create a Flyspray task for these bugs. I'm sure they are real, and if captured in Flyspray they will be addressed. Otherwise, we lose lots of drive-by bug reports. And we really want to catch them all.

Thanks
Dave