Help / FAQ

[dwiprasada]

Thanks for your prompt reply

Here i paste more log from hyperterminal
00,A,A*6B
$GPVTG,317.79,T,,M,0.02,N,0.04,K,A*30
$GPZDA,094025.00,23,01,2011,00,00*6E
$GPRMC,094025.00,A,0123.04020,N,10357.98483,E,0.02 ,317.79,230111,,,A*55
VTG,127.34,T,,M,0.04,N,0.07,K,A*3D
$GPZDA,094037.00,23,01,2011,00,00*6D
$GPRMC,094037.00,A,0123.04019,N,10357.98482,E,0.04 ,127.34,230111,,,A*53
00,A,A*63
$GPVTG,14.25,T,,M,0.01,N,0.01,K,A*0F
$GPZDA,094041.00,23,01,2011,00,00*6C
$GPRMC,094041.00,A,0123.04018,N,10357.98482,E,0.01 ,14.25,230111,,,A*67
VTG,205.38,T,,M,0.02,N,0.04,K,A*37
$GPZDA,094045.00,23,01,2011,00,00*68
$GPRMC,094045.00,A,0123.04017,N,10357.98482,E,0.02 ,205.38,230111,,,A*51
) VTG,174.13,T,,M,0.02,N,0.03,K,A*3C
$GPZDA,094054.00,23,01,2011,00,00*68
$GPRMC,094054.00,A,0123.04013,N,10357.98481,E,0.02 ,174.13,230111,,,A*5A
VTG,160.37,T,,M,0.01,N,0.01,K,A*3E
$GPZDA,094055.00,23,01,2011,00,00*69
$GPRMC,094055.00,A,0123.04013,N,10357.98481,E,0.01 ,160.37,230111,,,A*5B
`0,A,A*6D
$GPVTG,228.48,T,,M,0.02,N,0.04,K,A*3F
$GPZDA,094056.00,23,01,2011,00,00*6A
$GPRMC,094056.00,A,0123.04013,N,10357.98481,E,0.02 ,228.48,230111,,,A*5C
`0,A,A*6D
$GPVTG,267.54,T,,M,0.05,N,0.09,K,A*33
$GPZDA,094057.00,23,01,2011,00,00*6B
$GPRMC,094057.00,A,0123.04013,N,10357.98480,E,0.05 ,267.54,230111,,,A*5D
VTG,287.36,T,,M,0.04,N,0.08,K,A*39
$GPZDA,094101.00,23,01,2011,00,00*69
$GPRMC,094101.00,A,0123.04012,N,10357.98480,E,0.04 ,287.36,230111,,,A*55

what i see from there all sentence should be enough for opencpn get the position and etc.

[cagney]

Not only data missing.......
This line from the log caught my eye..

2:17:25 PM: AIS Data Source is....None

You have to set Toolbox->GPS->NMEA Data Source to the correct com port.
Have you read this: Setting Up GPS | Official OpenCPN Homepage?

Thomas

[dwiprasada]

Thomas,

I'm not connect the AIS with it, I'm Connected my GPS on com 1
Check the log again
2:17:25 PM: NMEA Data Source is....Serial:COM1

[cagney]

My bad!

Another thing, I'm learning a bit of NMEA, and it seems to me that there is something wrong with the GPRMC sentences.

$GPRMC,094055.00,A,0123.04013,N,10357.98481,E,0.01 ,160.37,230111,,,A*5B

The checksum is "5B" but ought to be "7B" if my calculation is correct.
Also, the "A" before the "*" should not be there as the previous fields are empty, and is wrong anyway, as an "E" or "W" are the only options.

I suppose that this points back to your GPS!

Thomas

[PjotrC]

Thomas, dwiprasada...

The checksum is wrong because of the unexpected blank inside the RMC line. Effectively the sentence reads

$GPRMC,094055.00,A,0123.04013,N,10357.98481,E,0.01

However, after extracting all RMC sentences and removing the offending blanks OCPN still does not like this input. PolarCOM displays position OK. So, there is something to investigate, but, please, let's have first a correct input stream...

Piotr

[champ8242]

I believe PolarCom (I know for sure NavMonPC) is not checking the checksum. Better to have (not completely) correct data then no data at all!?!? Up for discussion. Could become a checkbox.

Bart

[PjotrC]

After removing the erroneous blanks the checksums are OK, so it is something else...

The problem is in the file format, I think, or the method of feeding the data into OCPN, not the NMEA contents. I attach the file rectified by hand, with obviously wrong syntax removed and all correct lines kept verbatim. OpenCPN displays this correctly.

In my test the problem was (not a new one) with the CR/LF vs. CR/CR/LF sequence at every line end. This can happen when recording and replaying input from COM1, but the same stream should be OK when read directly from COM1 - if it is reasonably correct NMEA, of course.

As to whether allow or disallow skipping checksums - most nav software I know does indeed have a check-box for waiving the checksum. It would obviously help with testing and debugging new features. But for underway I think the checksums should be there. All equipment I use does produce correct checksums. Otherwise it is hard to draw the line, when to reject input - in dwiprasada's example "intelligent" software might in principle do it all - remove extra blanks, insert missing $GP in front of line, guess the position from scraps of syntax, etc... Nothing I ever see is 100% NMEA compliant, but the checksum seems a reasonable limit. So, I would prefer a DebugNMEAChecksum=1000 in the init file over a checkbox.

Piotr

[dacust]

Originally Posted by PjotrC

...
As to whether allow or disallow skipping checksums - most nav software I know does indeed have a check-box for waiving the checksum. It would obviously help with testing and debugging new features. But for underway I think the checksums should be there. All equipment I use does produce correct checksums. Otherwise it is hard to draw the line, when to reject input - in dwiprasada's example "intelligent" software might in principle do it all - remove extra blanks, insert missing $GP in front of line, guess the position from scraps of syntax, etc... Nothing I ever see is 100% NMEA compliant, but the checksum seems a reasonable limit. So, I would prefer a DebugNMEAChecksum=1000 in the init file over a checkbox.

Piotr

I agree.

As for me, I would rather hunt down a GPS that provides the correct information and leave the checksum on. But providing a way to get around that may be unavoidable for some users. Your idea of a conf tag is, in my mind, better than an easy checkbox.

-dan

[cagney]

Also, the "A" before the "*" should not be there as the previous fields are empty, and is wrong anyway, as an "E" or "W" are the only options.

This s what I wrote............and it is wrong. Not knowing, I used slightly outdated info from the net.
Later I found out that

NMEA version 2.3.added a mode indicator to many sentences to indicate what
kind of fix the receiver has. The value can be one of
A=autonomous
D=differential
E=Estimated
N=not valid,
S=Simulator.
Sometimes there can even be a null value as well.
The A and D are the only vales that will indicate an Active and reliable Sentence.
This mode character has been added to the end of RMC, RMB, VTG, and GLL sentences.
Optionally, to some others as well, including the BWC and XTE sentences.

I have now added this to the wiki.

dwiprasada
What kind of GPS do you have?

Thomas

[amadeus]

I wan't to install the celestial navigation plugin in OpenCPN. But can't find any info on how. Can Anyone help?

[cagney]

The old celestial plugin was never updated to the new plugin interface.
This is unfortunate as a celestial plugin for OpenCPN is a brilliant idea.
So,... at this time there is no Celestial plugin available. Hopefully this will change.

Thomas

[tiorico]

I'd like to try opencpn on my old Win98 laptop (Celeron 600) (yes, I know.... no lectures please). It does fine with non-inflated software.

Can someone tell me if the last version that supported 98 (ver. 2.1.0) is available for download anywhere? I've looked all over.

Thanks

[cagney]

Originally Posted by tiorico

I'd like to try opencpn on my old Win98 laptop (Celeron 600) (yes, I know.... no lectures please). It does fine with non-inflated software.

Can someone tell me if the last version that supported 98 (ver. 2.1.0) is available for download anywhere? I've looked all over.

Thanks

Source Forge has every version of OpenCPN ever published:OpenCPN - Browse /opencpn at SourceForge.net

Thomas

[tiorico]

Originally Posted by cagney

Source Forge has every version of OpenCPN ever published:OpenCPN - Browse /opencpn at SourceForge.net

Thomas

thanks, I found it.
Problem was, in case someone else is looking.... here's what happened:
Sourceforge tripped up Firefox 2.20 ( final W98 supported version) on the "Files" page. Using IE 8, I finally got the download, after only a couple sputters.

Thanks for all the good work you all do
-Rico

[AllezCat]

Hello,
have recently installed openCPN, and downloaded a few charts.
Looks great.
However I cannot connect the GPS.
Followed the instructions:

"Download the latest driver from Prolific - http://www.prolific.com.tw/Eng/downloads.asp?ID=31"

But, it has no results - doesn't show in ports(in fact there were no ports in device manager)
Using Windows 7 laptop, Garmin handheld GPS72H.
Any pointers?
thanks