Help / FAQ

[rgleason]

Stn92

Attached is the EBL Properties page, note the choices available may be quite useful in solving your problem.

Rotate with boat
Maintain with heading or course over ground
EBL angle (port/starboard)
EBL Fixed end position
Show VRM
Always show EBL information
Persistant

[stn92]

Two class B AIS transponders.

[rgleason]

Have you tried the plugin yet?

[nohal]

Originally Posted by stn92

Two class B AIS transponders.

Are you aware of their update frequency and accuracy? For docking a ship, I would expect something like at least a 10Hz high precision position/motion vector sources to be needed. Nothing like that is present in the class B equipment available on the market.

[stn92]

Originally Posted by rgleason

Have you tried the plugin yet?

Yes i did. Thanks. But drawing the speed vectors which moving with boat, rotating with it and etc. - is not such difficult. I already did it.
[SPOILER]

            drawVector(false,ownship.v22.x, ownship.v22.y, v22);
            drawVector(true, ownship.v21.x, ownship.v21.y, v21);
            drawVector(false, ownship.v12.x, ownship.v12.y, v12);
            drawVector(true, ownship.v11.x, ownship.v11.y, v11);

void drawVector(bool out,  int posx, int posy, const Vector& v) {
    if (v.value > 1){ //если значение вектора не меньше порогового значения
        posx = floor(posx)*scale_factor_x;
        posy = floor(posy)*scale_factor_y;
        int value = -v.value*cc1->GetVPScale()*0.25;
        int angle = v.angle;
        angle -= gCog; // компенсируем угол поворота судна
        if (angle < 0) angle += 360;
        glTranslatef(posx, posy, 0);
        glRotatef(angle, 0, 0, 1);

        glBegin(GL_LINES);
        glVertex2f(0, 0);
        glVertex2f(0, value);
        glEnd();
      
        if (out){
            glBegin(GL_LINES);
            glVertex2f(0, value);
            glVertex2f(-5, value + 6);
            glEnd();

            glBegin(GL_LINES);
            glVertex2f(0, value);
            glVertex2f(5, value + 6);
            glEnd();
        }
        else {

            glBegin(GL_LINES);
            glVertex2f(0, 0);
            glVertex2f(-5, -6);
            glEnd();

            glBegin(GL_LINES);
            glVertex2f(0, 0);
            glVertex2f(5, -6);
            glEnd();

        }

        glRotatef(-angle, 0, 0, 1);
        glTranslatef(-posx, -posy, 0);
    }
}

[/SPOILER]

Now I need to find the point of the nearest intersection with the boundary of the s57 object(land, mole etc.). Just need the point. Draw a line to this point and calculate the distance - this is not a problem.

[rgleason]

Nice, I guess you've got this figured out.

Perhaps look in weather_routing_pi code, where Sean figures out distance to GSHHS Background High Resolution and avoids land?

I could try to find that, but you're probably a lot faster at that than I am.

https://github.com/seandepagnier/weather_routing_pi

Would this become a new plugin?

[stn92]

Originally Posted by rgleason

Nice, I guess you've got this figured out.

I could try to find that, but you're probably a lot faster at that than I am.

I did not mean anything like that. I just wanted to say that my problem is not how to draw a vector. The language barrier greatly distorts the meaning. Sorry for wasting your time.

[stn92]

I figured out how to find closest intersection point with chart object.

This is the code. Maybe it will be useful to someone, too.

It retuns the lat/lon of the cosest intersection point with the specified object types on whole chart. The radius limitation does not work yet.

And example of using

std::vector<wxString> types = { "SLCONS", "LNDRGN", "LNDARE", "FLODOC", "PONTON" };
           
g_pi_manager->FindClosestObject(target_plugin_chart, gLat, gLon, 5, cc1->GetVP(), &minLat11, &minLon11, types);
      
dist11 = distance(gLat, gLon, minLat11, minLon11);

This is how it works. (not Paint this time)

[dnu]

Hello, and thank you for a brilliant piece of software!


Is there any interface in the plugin API to get information about a targeted ship in OpenCPN (the ship that I am currently Target Querying). Like the “Launcher” plugin (using SendPositionFixToAllPlugIns) can get information about my current position, I would like to use the “MMSI” of a random selected targeted ship, for quering information in an external source.


I have looked into the source code, but I have not been able to locate this interface.


Best regards, Daniel

[nohal]

Originally Posted by dnu

p { margin-bottom: 0.1in; line-height: 120%; } Hello, and thank you for a brilliant piece of software!


Is there any interface in the plugin API to get information about a targeted ship in OpenCPN (the ship that I am currently Target Querying). Like the “Launcher” plugin (using SendPositionFixToAllPlugIns) can get information about my current position, I would like to use the “MMSI” of a random selected targeted ship, for quering information in an external source.


I have looked into the source code, but I have not been able to locate this interface.


Best regards, Daniel

Daniel...
No, there currently is no such API. What exactly would be the usecase here? As in when exactly would the plugin get the information that "Something is needed to be done with MMSI xxxxxxxxx"

Anyway, probably ideal way to implement it is simply by sending an event through the SetPluginMessage API.

Very unfortunate you did not come a few days ago before 4.8.2 release, this development cycle will be big and long...

Pavel

[Hakan]

Originally Posted by dnu

Hello, and thank you for a brilliant piece of software!


Is there any interface in the plugin API to get information about a targeted ship in OpenCPN (the ship that I am currently Target Querying). Like the “Launcher” plugin (using SendPositionFixToAllPlugIns) can get information about my current position, I would like to use the “MMSI” of a random selected targeted ship, for quering information in an external source.


I have looked into the source code, but I have not been able to locate this interface.


Best regards, Daniel

Daniel..
There's a JSON message for AIS targets.
See: AIS_Decoder_cpp
Search for "AIS_Decoder::SendJSONMsg"

Example extract from one plugin(radar_pi): (But it's used in many plugins.)

void radar_pi::SetPluginMessage(wxString &message_id, wxString &message_body) {
if (message_id == wxS("AIS") ) {
      wxJSONReader reader;
      wxJSONValue message;
      if (!reader.Parse(message_body, &message)) {
        wxJSONValue defaultValue(999);
        long json_ais_mmsi = message.Get(_T("mmsi"), defaultValue).AsLong();
        if (json_ais_mmsi > 200000000) {  // Neither ARPA targets nor SAR_aircraft
          wxJSONValue defaultValue("90.0");
          double f_AISLat = wxAtof(message.Get(_T("lat"), defaultValue).AsString());
          double f_AISLon = wxAtof(message.Get(_T("lon"), defaultValue).AsString());
..............................

[Hakan]

Pavel is quicker and probably a better answer.

[nohal]

Originally Posted by Hakan

Daniel..
There's a JSON message for AIS targets.
See: AIS_Decoder_cpp
Search for "AIS_Decoder::SendJSONMsg"

Example extract from one plugin(radar_pi): (But it's used in many plugins.)

void radar_pi::SetPluginMessage(wxString &message_id, wxString &message_body) {
if (message_id == wxS("AIS") ) {
      wxJSONReader reader;
      wxJSONValue message;
      if (!reader.Parse(message_body, &message)) {
        wxJSONValue defaultValue(999);
        long json_ais_mmsi = message.Get(_T("mmsi"), defaultValue).AsLong();
        if (json_ais_mmsi > 200000000) {  // Neither ARPA targets nor SAR_aircraft
          wxJSONValue defaultValue("90.0");
          double f_AISLat = wxAtof(message.Get(_T("lat"), defaultValue).AsString());
          double f_AISLon = wxAtof(message.Get(_T("lon"), defaultValue).AsString());
..............................

Yes, very similar to this, just not for every AIS message received but for the queried target.
Until such a direct API is available you could likely work it around with the existing APIs by building a target list from the data above and implement own mouse event handling in the MouseEventHook to get what you want.

Pavel

[dnu]

Originally Posted by nohal

Yes, very similar to this, just not for every AIS message received but for the queried target.
Until such a direct API is available you could likely work it around with the existing APIs by building a target list from the data above and implement own mouse event handling in the MouseEventHook to get what you want.

Pavel

… Dear Pavel and Haken

Thank you for both suggestions, I will investigate them further. I might also abuse the “navobj.xml.changes” file for obtaining the information – when I start tracking a vessel, the MMSI is posted to this file along with coordinates for temporary storage. I can easily detect this and piggybag that way.

My application is a little “obscured” compared to “normal” usage of OpenCPN. I use OpenCPN as a monitor tool, for coarse alignment of a directional measurement radar – so click and align, its just a little project in the name of science :-) It relies on AIS and ADSB translated to AIS (SAR) via GnuRadio in an offline environment. So I basically return the MMSI (/translated ICAO) to a backend tool which filters the position information and use this for coarse alignment.

Best regards, Daniel

[nohal]

Originally Posted by dnu

…
Thank you for both suggestions, I will investigate them further. I might also abuse the “navobj.xml.changes” file for obtaining the information – when I start tracking a vessel, the MMSI is posted to this file along with coordinates for temporary storage. I can easily detect this and piggybag that way.

Now this is a VERY bad idea Not to mention it will break as soon as you turn off recording track of the AIS targets...