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Old 28-01-2013, 08:33   #1
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Want to beta test ocean currents gribs?

Over the weekend I got my server up and running to generate world wide current data in grib formats. The idea is you can view these on low-bandwidth connections like HF radio.

Remember I just finished this early this morning so I'm sure there are bugs!

To test it send an email to
query (AT) svsarana.com

in the message body put the lat/lon box you want current data for (the subject is ignored):

oscar:48N,38N,150W,140W

You'll get back a grib file that contains ocean currents for that area. Note that close to shore there is no data. The results are based on data generated by OSCAR Near realtime Global Ocean Surface Currents

I'm still having some quirky problems with some grib viewers. For example I don't think OpenCPN works, however Airmail's Viewfax works nicely.

Let me know if you find any problems or if you have any questions/suggestions about it.

Thanks,
Eric
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Old 28-01-2013, 10:36   #2
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Re: Want to beta test ocean currents gribs?

Hello Eric
thr request from your server works well.
The grib file seems not to be a valid grib file,
I tried to load the grib to qtvlm --> qtvlm crashes
to zygrib --> errormessage "not a valid grib file
to grib viewer from airmail --> shows up arrows, but only for 1 date/time stamp, not as suppost for a 5 days forecast

Great idea to make current gribs available for a selectable area.
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Old 28-01-2013, 12:36   #3
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Re: Want to beta test ocean currents gribs?

Yes, there seems to be a number of issues with viewers that I don't understand completely. I've asked a few people who create current gribs for help but no one has pointed out a problem.

For example compare your results to query@saildocs.com and put this in the body (this current model has limited coverage--not world-wide):
send rtofs:20N,25N,80W,90W|1,1|12|

It doesn't work on zyGrib and perhaps a few others. Most sailors where internet access is limited will be using airmail and viewfax which work.

I haven't been able to find a real difference in viewers. I could put the current on a wind layer instead of trying to use the correct GRIB definitions for current. I suspect this might be part of the problem. But I don't know for sure.
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Old 29-01-2013, 09:00   #4
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Re: Want to beta test ocean currents gribs?

I have modified one GRIB parameter to see if it makes a difference. Out of all of the ocean current gribs out there, none work on zyGrib and all work on Airmail's Viewfax. I've tried to emulate some of their settings.

Anyway I could use some more testers. Any GRIB experts out there? For people crossing equators or long distance sailors this is the only model the provides currents for much of the world, so I'm anxious to work all the kinks out of it.

send the following line to query (at) svsarana.com
oscar:48N,38N,150W,140W

You can put in whatever lat/lon values you want to look at for your area.
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Old 29-01-2013, 16:24   #5
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Re: Want to beta test ocean currents gribs?

Hi Eric,

When I send a RTOFS ocean current forecast request to Saildocs (For example: RTOFS:16N,09N,085W,077W), the file I get back opens readily in zyGrib with no problems. The attachments here will not take .grb files so I can't send you an example.

However, the file you sent me from the above query is not recognizable in zyGrib.

Perhaps this helps narrow down the problem?

Mark
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Old 29-01-2013, 19:33   #6
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Re: Want to beta test ocean currents gribs?

Thanks, but the Linux version of zyGrib definitely fails to open any other current files.

In lieu of any grib experts I guess I'll just have to accept that only viewfax and maxsea work. Viewfax is what most people use for HF gribs anyway.
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