Help / FAQ

[Indeed]

Hello,

I'm developing a plugin that depends on an external service which only communicates over gRPC (which uses HTTP2). After looking through /OpenCPN and /opencpn-libs, it looks like I'll have to create my own interface for bi-directional data transfer over gRPC. As the plugin API already supports downloading and POSTing over HTTP1 (see /opencpn-libs/api-a8/ocpn_plugin.h lines 1268-1358), I see no reason why a gRPC interface will be impossible.

Could you provide me any general advice for pulling this off? Things I should know relating to developing an OpenCPN API or maybe point to another plugin which does something similar.

Apologies for the open-ended and detail-sparse question, I'm still scoping this out and have little experience with OpenCPN; thought this was the best time to ask.

Thank you!

[nohal]

Forget about implementing gRPC from scratch using HTTP, there is by several orders of magnitude more stuff to it than the HTTP/2 transport.
Simply use https://github.com/grpc/grpc It is trivial to use as you can see for example in https://github.com/grpc/grpc/blob/ma...eter_client.cc

What plugin to point you to as example depends on what you actually want to do, if you want something really simple that does not do much, you may have a look for example at https://github.com/nohal/nsk_pi

[rgleason]

People should become familiar with the manual
FAQ Search https://opencpn.org/wiki/dokuwiki/do...nual_basic:faq
FAQ Support and Report https://opencpn.org/wiki/dokuwiki/do...support-report


Then they would not have so much trouble uploading.

[Bimbadeen]

Can you please advise the best source for up to date vector charts for South Pacific and SE Asia region, I have CM93 but looking for other options.
Many Thanks

[barcoMeCasa]

o charts have French Polynesia
https://o-charts.org/shop/en/oesenc/...polynesia.html

Also sat images can be an extremely useful and accurate resource anywhere slightly off the beaten track (or not)

https://www.youtube.com/watch?v=kCDP...FjLHEh&index=1

[Jon Hacking]

Originally Posted by Bimbadeen

Can you please advise the best source for up to date vector charts for South Pacific and SE Asia region, I have CM93 but looking for other options.
Many Thanks

Bimbadeen, as BarcoMeCasa pointed out, satellite imagery is often much better than vector charts. I can show you places where even the latest CM93v2 vector charts are out by a full mile.

Satellite imagery usually has max errors on the order of 3m. Amazing geo-registration. You can usually see into the water to a depth of 10-15m (30-50') to see reefs & to distinguish between coral & sand. Coral heads are easily visible, & they're exactly where plotted.

We've found that pretty much ALL of the commercial charts for SE Asia are pretty poor, displaced & low resolution, especially when you get away from population centers. So, since 2014, we've been making our own high-resolution charts.

After a nasty incident where a cruising boat was lost due to trusting their Navionics charts too much, we now publish our charts for cruisers to download. They include satellite imagery from ArcGIS, Bing, & Google, as well as nautical charts from CMap & Navionics. The nautical charts aren't as accurate, of course, but they have depths, which are certainly useful (although a practiced eye can usually tell depths with satellite imagery from the color of the water).

We currently cover the entire coastlines of over 30 countries, including the eastern Caribbean, Galapagos, Micronesia, Solomon Islands, much of SE Asia, much of the tropical Indian Ocean, & even some of tropical East Africa. The charts are in mbTiles format, which OpenCPN can now use, & they include all zoom levels from Z10-18, which is enough to see individual coral heads, or which slip you're in at a marina.

We're currently working on the South Pacific, but for now you'd be better served by going to our friend Bruce Balan's Chart Locker, as he's cruising those waters now.

Finally, if you want to make your own high-resolution charts, the tools & data are all free on the web. I publish a How-To guide to Making mbTiles that gives you step-by-step instructions.

Good luck!

[Bimbadeen]

Thankyou all for the helpful information, it is much appreciated,

[GrahamC]

OpenCPN 5.8.4 running on windows 10 has decided to make a mirror image of the window.
The normal window controls are on the left instead of the right.
Some of the context menu is in Arabic.
Charts are displayed as normal as is the info on the bottom.
The 'hover' text is displayed as a mirror image thus unreadable.
See Capture.jpg

All other apps and programs are working just fine.

Any ideas how to fix this apart from a clean install please?

[nohal]

What language do you have set for the user interface? If it is Arabic, switch to other language of your preference (English is just one higher in the list) and restart OpenCPN.

[GrahamC]

Originally Posted by nohal

What language do you have set for the user interface? If it is Arabic, switch to other language of your preference (English is just one higher in the list) and restart OpenCPN.

When I finally got to open settings - Yes It was set to Arabic.
I have no idea how this happened - I've been using this X86 onboard for the last 6 years and not had this problem.
Anyway Thank you it has saved a lot of trouble.

[GrahamC]

Track logged records obviously incorrect gps position.

I have noticed that when on passage and now when static at home the plotted track shows a divergence to zero degrees Longitude and or zero degrees latitude at times. I have ignored it up to now but thought it pertinent it the track was turned into a route.
As the gps has been in the same location for weeks now there must be some bad data getting through as it were, surely some logic should be applied here?
Checking GPS status flag ? and 3000 miles in 3 hours for a yacht making 5 to 7 knots or so should ring alarm bells?

Some thoughts on this please.

[Jon Hacking]

Graham, in your Options/Connect dialog, do you have the "Control checksum" box checked?

I'm not an OpenCPN Developer, but I think that box is supposed to reject sentences that have the wrong checksum. I would think that this would filter out any communications issues.

But as a WAG, I suspect you've got a poor GPS, & that it's not really OpenCPN's fault at all.

FWIW, we connect our AIS to OpenCPN. This not only gives us a good GPS signal, but also all our AIS targets. I have yet to see a better AIS display than OpenCPN, even from dedicated AIS displays, because it shows the targets against the background of your charts while also giving you complete control of alarms & display options.

[GrahamC]

Originally Posted by Jon Hacking

Graham, in your Options/Connect dialog, do you have the "Control checksum" box checked?

I'm not an OpenCPN Developer, but I think that box is supposed to reject sentences that have the wrong checksum. I would think that this would filter out any communications issues.

But as a WAG, I suspect you've got a poor GPS, & that it's not really OpenCPN's fault at all.

FWIW, we connect our AIS to OpenCPN. This not only gives us a good GPS signal, but also all our AIS targets. I have yet to see a better AIS display than OpenCPN, even from dedicated AIS displays, because it shows the targets against the background of your charts while also giving you complete control of alarms & display options.

Hi Jon, Yes the checksum option is checked (ticked in uk English!).

I am currently feeding GPS signal from my ICOM 423G which has its own GPS dangled out of the window.
At startup before it gets a fix it transmits RMC NMEA sentence with blank position data and the status symbol 'V' that denotes invalid fix.
When a fix is made it transmits the position and time and a status of 'A' at the end.

I have restarted the system many times with and without the radio on.
So I'm not sure what event caused the recording of the position with zero time and position data. ( I have seen this aboard but in a different environment.
I need to run the voyage data recorder or similar sniffer to trap the offending sentence.

I agree with you that the OPENCPN AIS display is the best of any system I have used.
I find it invaluable crossing the very busy English Channel.

FYI:
On Atlantis I have several GPS aerials
- Vesper AIS ,
- New GPS as a replacement for my trusty Raymarine aerial of 20 years ,
- One in the plotter C90W ( also suffering from epoch rollover).
- Garmin 128 - There as a bit of history and just in case!

I prioritise GPS feeds using an Actisense NDC-4 and can disable sources too.

This season it was mainly the AIS feed I was using for position data.

My ancient Skanti DSC radio complained about the rollover date and lack of ZDA NMEA sentence so I used the javascript plugin to fix this with a homemade script.
The date in the ZDA sentence was crafted from the PC UTC date time.
----
This is one of the reasons I have purchased a new radio - which has GPS , and NMEA in and out.

I have been working on a script to make DSC calls to ships in the AIS list Why ? - well sometimes they don't answer on 16 and because I can!

Graham

[wholybee]

Originally Posted by GrahamC

Hi Jon, Yes the checksum option is checked (ticked in uk English!).

I am currently feeding GPS signal from my ICOM 423G which has its own GPS dangled out of the window.
At startup before it gets a fix it transmits RMC NMEA sentence with blank position data and the status symbol 'V' that denotes invalid fix.
When a fix is made it transmits the position and time and a status of 'A' at the end.

I have restarted the system many times with and without the radio on.
So I'm not sure what event caused the recording of the position with zero time and position data. ( I have seen this aboard but in a different environment.
I need to run the voyage data recorder or similar sniffer to trap the offending sentence.

I agree with you that the OPENCPN AIS display is the best of any system I have used.
I find it invaluable crossing the very busy English Channel.

FYI:
On Atlantis I have several GPS aerials
- Vesper AIS ,
- New GPS as a replacement for my trusty Raymarine aerial of 20 years ,
- One in the plotter C90W ( also suffering from epoch rollover).
- Garmin 128 - There as a bit of history and just in case!

I prioritise GPS feeds using an Actisense NDC-4 and can disable sources too.

This season it was mainly the AIS feed I was using for position data.

My ancient Skanti DSC radio complained about the rollover date and lack of ZDA NMEA sentence so I used the javascript plugin to fix this with a homemade script.
The date in the ZDA sentence was crafted from the PC UTC date time.
----
This is one of the reasons I have purchased a new radio - which has GPS , and NMEA in and out.

I have been working on a script to make DSC calls to ships in the AIS list Why ? - well sometimes they don't answer on 16 and because I can!

Graham

I also sometimes get invalid GPS data into OCPN. In my case I have tracked it down to 2 things. First is my Vesper AIS will sometimes give a position of 0N 0E. Second, my Yacht Devices YDWG-02 will sometimes corrupt that sentence during the nmea2000 to nmea0183 translation and require a restart. Neither is OCPN's fault, but it would be nice if OCPN filtered the data based on impossible boat speeds.

[GrahamC]

Hi Warren,
That's very interesting as we both have a Vesper AIS.
As I am currently in the zone with javascript I will add a check on RMC sentences containing zero lat or long. Neither of which are in my normal cruising range.
It won't however stop OCPN recording it in the track unless a pre filter of some kind is installed.
Graham