How do I refresh a google map without affecting polylines

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C#

Google

mapping

Hi am developing a project with google map. In this i want to show the particular vehicle latitude and longitude. And put markers for each lat and lng. And also draw a polyline.

Now i have to refresh the map in 5 seconds. In this my polyline affecting, not showing in good. This is my code

var markers = [];
function submit() {
markers = [];
$.ajax({
url: "/map/GetLatitudeValues",
type: 'post',
dataType: 'json',
// imei:null,
data: {imei: $("#imei").val()},
async: false,
success: function (data) {
var Objects = data;
for (var key in Objects) {
markers.push({"lat": Objects[key].Latitude, "lng": Objects[key].Longitude});
}
},
error: function (XMLHttpRequest, textStatus, errorThrown) {
alert("Status: " + textStatus); alert("Error: " + errorThrown);
}
}); loadmap();
setInterval("submit()", 5000);
// loadmap();
}
$(document).ready(function () {

});

function loadmap() {
var mapOptions = {
center: new google.maps.LatLng(markers[0].lat, markers[0].lng),
zoom: 10,
mapTypeId: google.maps.MapTypeId.ROADMAP
};
var map = new google.maps.Map(document.getElementById("dvMap"), mapOptions);
var lat_lng = new Array();
var latlngbounds = new google.maps.LatLngBounds();

for (i = 0; i < markers.length; i++) {
var data = markers[i]
var myLatlng = new google.maps.LatLng(data.lat, data.lng);
lat_lng.push(myLatlng);
var marker = new google.maps.Marker({
position: myLatlng,
map: map
});
latlngbounds.extend(marker.position);
(function (marker, data) {
var infoWindow = new google.maps.InfoWindow({ content: $("#imei").val() + 'Latitude : ' + data.lat + 'Longitude : ' + data.lng});
google.maps.event.addListener(marker, "click", function (e) {
google.maps.event.trigger(map, 'resize');
infoWindow.open(map, marker);
});

})(marker, data);

}
map.setCenter(latlngbounds.getCenter());
map.fitBounds(latlngbounds);

//Initialize the Path Array
var path = new google.maps.MVCArray();

//Initialize the Direction Service
var service = new google.maps.DirectionsService();

//Set the Path Stroke Color

var poly = new google.maps.Polyline({ map: map, strokeColor: '#4986E7' });
// var path = poly.getPath();
// path.push(new google.maps.LatLng(data.lat,data.lng));
for (var i = 0; i < lat_lng.length; i++) {
if ((i + 1) < lat_lng.length) {
var src = lat_lng[i];
var des = lat_lng[i + 1];
poly.setPath(path);
service.route({
origin: src,
destination: des,
travelMode: google.maps.DirectionsTravelMode.TRANSIT
},
function (result, status) {
if (status == google.maps.DirectionsStatus.OK) {
for (var i = 0, len = result.routes[0].overview_path.length; i < len; i++) {

path.push(result.routes[0].overview_path[i]);
}
}
});
}
}
}
</script>


<input type ="text" id="imei" name="imei" />
<input type="button" value="submit" onclick="submit()" />
Please any one help with this...