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Old 28-11-2017, 21:13   #76
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Re: New Plugin NmeaConvertor

zzz, Please let us know if your formula works, then we'll add it to to the documentation for others to use. Thanks.
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Old 28-11-2017, 22:34   #77
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Re: New Plugin NmeaConvertor

Here is the page, I've added the formula now, but would be very interested in confirmation of the result.

https://opencpn.org/wiki/dokuwiki/do...as_conversions
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Old 09-12-2017, 02:30   #78
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Re: New Plugin NmeaConvertor

Here’s the version actually worked;

$XXMWV,$WIMWV1+180*acos((sqr($WIMWV3)+(sqr($GPRMC7 )+sqr($WIMWV3)-2*$GPRMC7*$WIMWV3*cos($WIMWV1*3.14159265/180))-sqr($GPRMC7))/(2*sqrt(sqr($GPRMC7)+sqr($WIMWV3)-2*$GPRMC7*cos($WIMWV1*3.14159265/180))*$WIMWV3))/3.14159265,T,sqrt(sqr($GPRMC7)+SQR($WIMWV3)-2*$GPRMC7*$WIMWV3*cos($WIMWV1*3.14159265/180)),N,A

1. $s were missing inthe previous version
2. Changed wind speed unit from K to N
3. Deleted spaces after commas
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Old 09-12-2017, 17:04   #79
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Re: New Plugin NmeaConvertor

Thanks ZZZ, have updated
https://opencpn.org/wiki/dokuwiki/do...nmea_converter
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Old 15-12-2017, 19:54   #80
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Re: New Plugin NmeaConvertor

1) It would be nice if instead of using sqr() we could support the ^ operator.
2) if we could replace PI rather than writing 3.14... everywhere.
3) Another thing would be to more easily match nmea input sentences, so the formulas will work for any instruments ... eg **MWV It might be complicated if it can match its own outputs from a different rule though
4) A user interface to include many builtin convenience converters, like ones for pressure, or for wind.


I tried this plugin to convert apparent wind to true wind with the above mentioned formula.

True wind direction is relative to the boat. This can be useful, but what if I want to compute true wind relative to north?

Now... is there a nmea sentence for true wind relative to north, or is it only for the boat? I can't seem to find this.


To do this requires a bearing sensor which I have as well, and to compute the magnetic deviation which the wmm plugin provides.

It should therefore be possible to sit at anchor, and create a watchdog alarm for when the actual wind direction clocks past a certain angle.
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Old 15-12-2017, 21:45   #81
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Re: New Plugin NmeaConvertor

Nice ideas Sean.
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Old 16-12-2017, 01:31   #82
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Re: New Plugin NmeaConvertor

@Sean,
Later this winter I'll have a look again at this plugin. (First complete a compass deviation PI)
I am using a library for the calculation(ec_engine), and I dont't like to mess around in that one for adding functions.
Before sending a sentence to the calculator engine all variables are replaced by the one's collected from the input nmea. It would be easy to add here a PI->3.14.. substitute.
Using wildcards in the input should also be not to difficult, but could make it more difficult to debug the formula.
I see no reason why you can't make a fake inbetween sentence, and use that one again in a next formula. It will cause some time delay however.

The plan is to also make it possible to use identifiers including the first field. As some none standard sentences use the first field as part of identity.
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Old 16-12-2017, 08:48   #83
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Re: New Plugin NmeaConvertor

Also... Correct me if I'm wrong, but the above true wind calculation is technically incorrect.


This is because it only uses GPS speed. This would be fine, if the boat (or wind sensors) were aligned to be pointed exactly the direction it were moving (gps course), but this isn't the case. The boat might be moving sideways a bit. It should use gps course as well, but it also needs to know the true bearing (compass corrected from magnetic deviation)


Maybe the difference is slight in a lot of cases, only few degrees if that, but I wanted to point it out.


At least, it should filter the GPS speed down considerably because gps speed is often erratic, but averages out. A water speed sensor would be nicer.
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Old 16-12-2017, 13:33   #84
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Re: New Plugin NmeaConvertor

Excellent point Sean, speedo is better than GPS SOG.
The Windows Polar program Polauto by Patrick Tiercelin has several choices for input data, but the speedo is the favored one.
https://opencpn.org/wiki/dokuwiki/do...ware:polauto&s[]=polauto

[QUOTE]
Also... Correct me if I'm wrong, but the above true wind calculation is technically incorrect.

This is because it only uses GPS speed. This would be fine, if the boat (or wind sensors) were aligned to be pointed exactly the direction it were moving (gps course), but this isn't the case. The boat might be moving sideways a bit. It should use gps course as well, but it also needs to know the true bearing (compass corrected from magnetic deviation)

Maybe the difference is slight in a lot of cases, only few degrees if that, but I wanted to point it out.

At least, it should filter the GPS speed down considerably because gps speed is often erratic, but averages out. A water speed sensor would be nicer.[/QUOTE]

See what Thomas [Tactics_pi] does about True Wind for data

https://opencpn.org/wiki/dokuwiki/do...ools:tactics&s[]=tactics#calculate_true_wind_data
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Old 11-01-2018, 02:23   #85
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Re: New Plugin NmeaConvertor

Hello, im struggeling to install this plugin on my opencpn /raspberry pi setup
The package location seems to be missing.
Please help linux experts
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Old 14-01-2018, 01:44   #86
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Re: New Plugin NmeaConvertor

Quote:
Originally Posted by Ontrackx View Post
Hello, im struggeling to install this plugin on my opencpn /raspberry pi setup
The package location seems to be missing.
Please help linux experts
I am NO expert, but as there is no answer to your plea...
Here is my build of the deb package (use (eg) gdebi to install)
DL.FREE.FR

It will install the .so file in /usr/local/lib/opencpn... If your opencpn is in /usr/share... you'll have to move it there (possibly also the .mo files in /usr/local/share/locale/...)

BUT A quick test as in
https://opencpn.org/wiki/dokuwiki/do...nmea_converter
FAILED
But I may have had my parameters wrong
Please report if you succeed...
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Old 14-01-2018, 16:26   #87
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Re: New Plugin NmeaConvertor

Maybe it needs a tag or something. I'd check the github location and see if there are any tags in the commits, or even some release numbers might work. (Linux users chime in, a windows guy is speaking)

Quote:
Originally Posted by Ontrackx View Post
Hello, im struggeling to install this plugin on my opencpn /raspberry pi setup
The package location seems to be missing.
Please help linux experts
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Old 14-01-2018, 17:59   #88
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Re: New Plugin NmeaConvertor

https://github.com/RooieDirk/NmeaCon...commits/master

No there are no version numbers in the commit and there are no released numbered either. I understand this makes it hard for you Linux guys as Launchpad and others won't find it.

The above is probably half truths and lies, and Pavel will hopefully correct me!
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