How to know if someone lost or still on track with Google Maps Response?

Projects General Guidance
1

So I have a project with GPS module and I want to search route with Google Maps. I have done implementing GPS with Google Maps, but now I come into a problem. I don't know if user still on track.

I get this array of steps from API Response:

 "steps" : 
               [
                  {
                     "distance" : 
                     {
                        "text" : "50 m",
                        "value" : 50
                     },
                     "duration" : 
                     {
                        "text" : "1 min",
                        "value" : 39
                     },
                     "end_location" : 
                     {
                        "lat" : -7.282490199999999,
                        "lng" : 112.7951477
                     },
                     "html_instructions" : "Head \u003cb\u003esoutheast\u003c/b\u003e",
                     "polyline" : 
                     {
                        "points" : "phmk@ufmoTr@o@JO"
                     },
                     "start_location" : 
                     {
                        "lat" : -7.2821734,
                        "lng" : 112.7948261
                     },
                     "travel_mode" : "WALKING"
                  },
...

Above is the example of 1 steps. Currently, I take the latitude and longitude and using Harvine Formula to find the distance from the GPS to the end_location. I use this function to count distance:

// Count distance in meters
double getDistanceInM(double lat1, double lon1, double lat2, double lon2) {
    double R =  6335439; // Radius of the earth in m
    double dLat = deg2rad(lat2 - lat1);  // convert degrees to radians
    double dLon = deg2rad(lon2 - lon1);
    double a = sin(dLat/2) * sin(dLat/2) +
               cos(deg2rad(lat1)) * cos(deg2rad(lat2)) *
               sin(dLon/2) * sin(dLon/2);
    double c = 2 * atan2(sqrt(a), sqrt(1-a));
    double d = R * c; // Distance in m
    return d;
}

After that I wait till the distance is below 5m before I instruct a new route to the user.

But how to know if user walking in the intended route. What if the user miss a turn. How can I know this?

I thought about counting distance between this step end_location and next step end_location. I thought that user should be closer to this step end_location then next_step end location, but I don't think this is the right way to do it

2

assuming you have straight (great circle) path between two way points, what you need to track is known as XTE in GPS terminology ➜ the Cross Track Distance

see my post

➜ you'll know if you are left or right of the ideal path and have the distance to that path

3

Wow that's what I need. Thanks for the answer

4

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