Displaying Signal K API values in Node-RED

[cybardev]

I have the following flow in Node-RED:

Click to view JSON...

[
    {
        "id": "0cadd5ea4f5be27e",
        "type": "tab",
        "label": "Flow 1",
        "disabled": false,
        "info": "",
        "env": []
    },
    {
        "id": "e644ddfbe936d292",
        "type": "signalk-on-delta",
        "z": "0cadd5ea4f5be27e",
        "name": "[self] Location Data",
        "context": "vessels.self",
        "flatten": true,
        "x": 130,
        "y": 120,
        "wires": [
            [
                "04409d7fef7f95b0",
                "8e1d736d0ab5be67",
                "25f83e73f72f52d3",
                "d158c1fa4364385d"
            ]
        ]
    },
    {
        "id": "6c35a75c863e0f70",
        "type": "ui_text",
        "z": "0cadd5ea4f5be27e",
        "group": "cc3cbcae8a4cb332",
        "order": 1,
        "width": "0",
        "height": "0",
        "name": "",
        "label": "latitude",
        "format": "{{msg.payload}}",
        "layout": "row-spread",
        "className": "",
        "x": 600,
        "y": 60,
        "wires": []
    },
    {
        "id": "566fa65bf263a78e",
        "type": "ui_text",
        "z": "0cadd5ea4f5be27e",
        "group": "cc3cbcae8a4cb332",
        "order": 2,
        "width": "0",
        "height": "0",
        "name": "",
        "label": "longitude",
        "format": "{{msg.payload}}",
        "layout": "row-spread",
        "className": "",
        "x": 600,
        "y": 100,
        "wires": []
    },
    {
        "id": "04409d7fef7f95b0",
        "type": "change",
        "z": "0cadd5ea4f5be27e",
        "name": "latitude",
        "rules": [
            {
                "t": "set",
                "p": "payload",
                "pt": "msg",
                "to": "payload.latitude",
                "tot": "msg"
            }
        ],
        "action": "",
        "property": "",
        "from": "",
        "to": "",
        "reg": false,
        "x": 340,
        "y": 60,
        "wires": [
            [
                "15a81e1eb1bb1be3"
            ]
        ]
    },
    {
        "id": "8e1d736d0ab5be67",
        "type": "change",
        "z": "0cadd5ea4f5be27e",
        "name": "longitude",
        "rules": [
            {
                "t": "move",
                "p": "payload.longitude",
                "pt": "msg",
                "to": "payload",
                "tot": "msg"
            }
        ],
        "action": "",
        "property": "",
        "from": "",
        "to": "",
        "reg": false,
        "x": 340,
        "y": 100,
        "wires": [
            [
                "4a32ae5ee87dcca0"
            ]
        ]
    },
    {
        "id": "15a81e1eb1bb1be3",
        "type": "function",
        "z": "0cadd5ea4f5be27e",
        "name": "5dp",
        "func": "if (msg.payload != null) {\n    msg.payload = msg.payload.toFixed(5);\n}\nreturn msg;",
        "outputs": 1,
        "noerr": 0,
        "initialize": "",
        "finalize": "",
        "libs": [],
        "x": 470,
        "y": 60,
        "wires": [
            [
                "6c35a75c863e0f70"
            ]
        ]
    },
    {
        "id": "4a32ae5ee87dcca0",
        "type": "function",
        "z": "0cadd5ea4f5be27e",
        "name": "5dp",
        "func": "if (msg.payload != null) {\n    msg.payload = msg.payload.toFixed(5);\n}\nreturn msg;",
        "outputs": 1,
        "noerr": 0,
        "initialize": "",
        "finalize": "",
        "libs": [],
        "x": 470,
        "y": 100,
        "wires": [
            [
                "566fa65bf263a78e"
            ]
        ]
    },
    {
        "id": "25f83e73f72f52d3",
        "type": "function",
        "z": "0cadd5ea4f5be27e",
        "name": "location (self)",
        "func": "if (msg.payload != null) {\n    msg.payload.name = \"self\";\n}\nreturn msg;",
        "outputs": 1,
        "noerr": 0,
        "initialize": "",
        "finalize": "",
        "libs": [],
        "x": 350,
        "y": 180,
        "wires": [
            [
                "e0ec963913cbf7a9",
                "de5c4044.d4e0f"
            ]
        ]
    },
    {
        "id": "de5c4044.d4e0f",
        "type": "worldmap-tracks",
        "z": "0cadd5ea4f5be27e",
        "name": "Path (self)",
        "depth": "5",
        "layer": "combined",
        "smooth": false,
        "x": 540,
        "y": 140,
        "wires": [
            [
                "e0ec963913cbf7a9"
            ]
        ]
    },
    {
        "id": "e0ec963913cbf7a9",
        "type": "ui_worldmap",
        "z": "0cadd5ea4f5be27e",
        "group": "cc3cbcae8a4cb332",
        "order": 4,
        "width": "8",
        "height": "8",
        "name": "Map",
        "lat": "",
        "lon": "",
        "zoom": "",
        "layer": "OSMC",
        "cluster": "",
        "maxage": "",
        "usermenu": "hide",
        "layers": "hide",
        "panit": "false",
        "panlock": "false",
        "zoomlock": "false",
        "hiderightclick": "true",
        "coords": "none",
        "showgrid": "true",
        "allowFileDrop": "false",
        "path": "/worldmap",
        "overlist": "DR,CO,RA,DN,SN,HM",
        "maplist": "OSMG,OSMC,EsriC,EsriS,EsriT,EsriO,EsriDG,NatGeo,UKOS,OpTop",
        "mapname": "",
        "mapurl": "",
        "mapopt": "",
        "mapwms": false,
        "x": 750,
        "y": 200,
        "wires": []
    },
    {
        "id": "d158c1fa4364385d",
        "type": "function",
        "z": "0cadd5ea4f5be27e",
        "name": "location (audio)",
        "func": "if (msg.payload != null) {\n    msg.payload.name = \"audio\";\n    msg.payload.latitude += 0.1;\n    msg.payload.longitude += 0.1;\n}\nreturn msg;",
        "outputs": 1,
        "noerr": 0,
        "initialize": "",
        "finalize": "",
        "libs": [],
        "x": 340,
        "y": 220,
        "wires": [
            [
                "e0ec963913cbf7a9",
                "617d1bd54133a094"
            ]
        ]
    },
    {
        "id": "61eeee703dbe89fb",
        "type": "comment",
        "z": "0cadd5ea4f5be27e",
        "name": "Location View",
        "info": "",
        "x": 130,
        "y": 80,
        "wires": []
    },
    {
        "id": "617d1bd54133a094",
        "type": "worldmap-tracks",
        "z": "0cadd5ea4f5be27e",
        "name": "Path (audio)",
        "depth": "5",
        "layer": "combined",
        "smooth": false,
        "x": 550,
        "y": 260,
        "wires": [
            [
                "e0ec963913cbf7a9"
            ]
        ]
    },
    {
        "id": "cc3cbcae8a4cb332",
        "type": "ui_group",
        "name": "Location",
        "tab": "0550edd77a3f3e78",
        "order": 1,
        "disp": true,
        "width": "8",
        "collapse": false,
        "className": ""
    },
    {
        "id": "0550edd77a3f3e78",
        "type": "ui_tab",
        "name": "Home",
        "icon": "dashboard",
        "disabled": false,
        "hidden": false
    }
]

However, if I flatten the signalk-on-delta node, it only gives latitude and longitude (which works in this example cuz I'm only needing those, but I need other info too). All other information is lost. I want to take in all the info without flattening it and then manually filter it into position, and whatever else I need (example: https://localhost:3443/signalk/v1/api/vessels/self/audio/).

An alternative would be to GET the full model from the server API and process it manually, but I feel like that isn't ideal.

So, how can I get the value of paths like https://localhost:3443/signalk/v1/api/vessels/self/audio/ as an automatically updating delta node?

[tkurki]

Flatten does not only give you latitude and longitude, it "flattens" data so that a single Signal K Delta message with multiple values like

{
  "context": "vessels.urn:mrn:imo:mmsi:234567890",
  "updates": [
    {
      "source": {
        "label": "N2000-01",
        "type": "NMEA2000",
        "src": "017",
        "pgn": 127488
      },
      "timestamp": "2010-01-07T07:18:44Z",
      "values": [
        {
          "path": "propulsion.0.revolutions",
          "value": 16.341667
        },
        {
          "path": "propulsion.0.boostPressure",
          "value": 45500
        }
      ]
    }
  ]
}

will result in one Node-RED message for each value.

signalk-on-delta node will give you all the data. If you want data for a specific path use https://github.com/SignalK/node-red-embedded#signalk-subscribe node.

[cybardev]

Used subscribe node and that does what I want. I can just get the data I need individually.

Thank you very much 😊

[cybardev]

Loosely related but what do you feel would be the most "aligned with Signal K philosophy" way to get data (MMSI, Vessel Class, GPS lat/lon, Distance to Target from self) on the nearest AIS target? Currently I'm doing this (not returning lat/lon in this version but can be included with slight modification):

getNearestVessel(vessels) {
    let ownPos = {};
    let distances = {};
    let nearestVessel = { mmsi: "", vesselClass: "", distance: 0.0 };

    // get distance from self to global origin
    Object.entries(vessels).forEach((vessel) => {
        let [name, data] = vessel;
        if (
            name.startsWith("urn:mrn:signalk:uuid:") &&
            data.navigation.position != null
        ) {
            ownPos = data.navigation.position.value;
            return;
        }
    });

    // get distance from self to nearby vessels
    Object.entries(vessels).forEach((vessel) => {
        let [name, data] = vessel;
        if (
            !name.startsWith("urn:mrn:signalk:uuid:") &&
            data.navigation.position != null
        ) {
            distances[name] = this.getVesselDistance(
                ownPos,
                data.navigation.position.value
            );
        }
    });

    // find nearest vessel info
    nearestVessel.distance = Math.min(...Object.values(distances));
    Object.entries(distances).forEach((vessel) => {
        let [name, distance] = vessel;
        if (distance === nearestVessel.distance.toString()) {
            nearestVessel.mmsi = name.split(":")[4];
        }
    });

    // get vessel class
    const ID = "urn:mrn:imo:mmsi:" + nearestVessel.mmsi;
    if (vessels[ID] != null) {
        nearestVessel.vesselClass = vessels[ID].sensors.ais.class.value;
    }

    return nearestVessel;
}

Here I pass the entire vessels/ JSON response as an argument and process the whole thing manually. What might be a better way?

PS: getVesselDistance(selfPos, targetPos) is just the haversine function. This is also not yet being done in Node-RED and I'm trying to make it work with Node-RED. I made this in a custom dashboard.

---

UPDATE: I'm considering injecting a custom data blob ({ id: mmsi, vesselClass: classValue, distance: value, pos: [lat, lon] }) into vessels.self.ais.nearestTarget or some path and subscribing to that. The injection will be done in a Python script as was discussed in #64.

[tkurki]

Maybe create a separate discussion for this?I don't think this has much to do with the original topic.