GPS modul. How to get speed and put it in variable?

Hi guys!
I want to get the speed and, depending on it do an actions, for example, to light the LED.
I see 2 ways of solving this problem.
the first one
Use the standard Esprino library, taken from the link below.
https://www.espruino.com/GPS

Serial3.setup (115200, {rx: P0, tx: P1});
var gps = require ("GPS"). connect (Serial3, function (data) {
  console.log (data);
});

The following data is displayed:

{"time": "16:35:29", "lat": 53.068403, "lon": - 4.076282, "fix": 1, "satellites": 7, "altitude": 1085.0}

There is no speed but I can get it if i know Time1 and Time0 and latitude, longitude at Time1, Time0.
I can colculat the distance pased using formulas from there http://www.movable-type.co.uk/scripts/la­tlong.html.

, then devide it on diff betvin T1 and T0

The problem is

How get latitude, longitude at T1, T0 from this code?
Serial3.setup (115200, {rx: P0, tx: P1});
var gps = require ("GPS"). connect (Serial3, function (data) {
  console.log (data);
});
if i try somth like this

Serial3.setup(115200, {rx: P0, tx: P1});
var gps = require("GPS").connect(Serial3, function(data) {
  T1=data;
return T1;
})
console.log(gps)enter code here

i get empty valus in console.

.
the second way is to communicate with serial
I use such cod

Serial3.setup (115200, {rx: P0, tx: P1});
var bufer = '';
Serial3.on ('data', function (data) {
bufer + = data;
var lines = bufer.split ('$');
bufer = lines [lines.length-1];
if (lines.length> 1) {
for (l = 0; l <lines.length-1; l ++) {print (lines [l]);}}});

Problem
As a result, it get all data from GPS controller but here http://www.gpsinformation.org/dale/nmea.­htm
I have not found any messages with such codes, and accordingly I do not understand what position, what it means, and how it's to pars it to get the speed. How to pars the
NMEA sentent ?

I think something like this will do what you want:

Serial3.setup (115200, {rx: P0, tx: P1});
var lastData;
var gps = require ("GPS"). connect (Serial3, function (data) {
  console.log (data);
  if (lastData) {
   // do stuff here - eg. the difference between the two readings
    var dlat = data.lat - lastData.lat;
    var dlon = data.lon - lastData.lon;   
  }
  lastData = data;
});

Although as you say, you might be able to extract the data that you want from other NMEA data. For instance VTG - Velocity made good sounds promising

Wow great. it works!!!

Serial3.setup (115200, {rx: P0, tx: P1});
var lastData;
var gps = require ("GPS"). connect (Serial3, function (data) {
  
  if (lastData) {
   // do stuff here - eg. the difference between the two readings
    var dlat =data.time;
 //   var dlon = data.lon - lastData.lon;   
  console.log (dlat);
 console.log ('*->',lastData);
 
  }
  

  lastData = data.time;
 // return lastData;
});

In general, going on the path 1 with yours help, I wrote such code, but there are some strange mistakes = (such as 45 km / h at rest). I tested it in my car. Visually it coincides with the speedometer in my smartphone =)

//********* 
Serial3.setup (115200, {rx: P0, tx: P1});

var R = 6371e3; //
var Led= require('@amperka/led').connect(A1);

var lastData; // 
var lastData2; //
var lastLon;  //  
var lastLat; //  
var LastTime;
var toRad=Math.PI/180;
var i=0;


var gps = require ("GPS"). connect (Serial3, function (data) {
  
  if (lastData,i<50) {
   // do stuff here - eg. the difference between the two readings
  //****** distance calc  
    var Lon=data.lon*toRad; // lon в  t1
    var Lat=data.lat*toRad; //lat в  t1
    var diffLon=Math.abs(Lon-lastLon*toRad);
    var diffLat= Math.abs(Lat-lastLat*toRad);
        var a= Math.sin(diffLat/2) * Math.sin(diffLat/2) +
        Math.cos(Lat) * Math.cos(lastLat*toRad) *
        Math.sin(diffLon/2) * Math.sin(diffLon/2);
    
    var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var distansP = R * c;
//****** time diff
var tTime= data.time.split(':'); // time array
tTime=tTime[2];
var diffTime=tTime-LastTime;
    //****** speed
    var speed1= distansP/diffTime; // m/s
    var speed2= speed1*3.6; // km/h 
    
    if(speed2>60){
      
      Led.turnOn();
    }
    else{Led.turnOff();}
 console.log(speed2,speed1);
 //console.log ('1',Math.sin(diffLat/2),diffLat/2,'2',M­ath.cos(Lat),  '3',Math.cos(lastLat*toRad),lastLat*toRa­d,'4',Math.sin(diffLon/2),'5',Math.sin(d­iffLon/2),'6',Math.sqrt(a),a,'7',Math.sq­rt(1-a),'8',diffTime ); Debugging
 
  }
  
lastData=data;
lastLon=data.lon; // in degrees

lastLat=data.lat; //in degrees


LastTime=  data.time.split(':');
LastTime= LastTime[2];  
  
//  lastData = data.time.split(':');
//lastData2 = lastData[2];
//  lastLon= data.lon;
  i=i+1;
 
});