Experiment with Location, geofencing, and a MQTT button

TL;DR, This Saturday I did experiment with my Node-RED server and some geo fencing APIs.

I create a location-sensitive button; when a user's mobile is inside the geo-fencing (red circle), the lamp glows up, and once the user's mobile goes out, the lamp glows down.

I used one open-source library to achieve this: node-red-contrib-world-map.

The node-red-contrib-web-worldmap 5.1.2 is a popular Node-RED node that allows you to display geographical data on an interactive world map within your Node-RED flows. and some JavaScript code snippets. Like

// Function node code

var circleData = flow.get("circleData");

var circleLat = circleData.lat;
var circleLon = circleData.lon;
var circleRadius = circleData.radius;

var currentLat = msg.payload.lat;
var currentLon = msg.payload.lon;

if (circleData && msg.payload) {


function calculateDistance(lat1, lon1, lat2, lon2) {
    // Haversine formula (approximate distance)
    var R = 6371e3; // Earth radius in meters
    var dLat = (lat2 - lat1) * Math.PI / 180;
    var dLon = (lon2 - lon1) * Math.PI / 180;
    var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
        Math.cos(lat1 * Math.PI / 180) * Math.cos(lat2 * Math.PI / 180) *
        Math.sin(dLon / 2) * Math.sin(dLon / 2);
    var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
    return R * c;
}

var distance = calculateDistance(circleLat, circleLon, currentLat, currentLon);

if (distance <= circleRadius) {
    msg.payload = { inside: true, distance: distance , radius: circleRadius};
} else {
    msg.payload = { inside: false, distance: distance ,radius: circleRadius };
}
}else{
    node.error = "somthing went wrong"
}
return msg;
        

The idea is completely based on the Haversine formula , with this help, I create the above method, which returns an object containing a boolean (which tells if the mobile is inside the geofencing or outside), the distance of the mobile (GPS device) from the center (geofencing), and the radius of geofencing.

If the mobile is inside the fencing, then the lamp glows up and vice versa.

Use case:

1. Home automation: We can use this setup in home automation. When some person comes inside the house, the garden light turns on and turns off in a vice versa situation.
2. Lock and unlock: The same setup can be used to lock and unlock the home doors.

If you are an IoT hobbyist and you have the knowledge of Node-RED, then you can use my work by downloading my workflow in the given link.

https://gist.github.com/iamrajendraverma/bc6d1bb4252bf8e299396f57f84ec74c

If you want to lean IOT with me, then you can message me at linkedin