Google Marker - Input

Front-end JavaScript
,
#1

Não consigo entender por que o javascript nao consegue pegar os valores no input?
Codigo - http://pastebin.com/GwHkyNmX

<form id="formulario">
    < div class="lugar">
        < div class="lginput">
            < label for="nome">Latitude</label>
            < input type="text" id="latitude" name="latitude" placeholder="-14.6915082" required="">
        < /div>
        < div class="lginput">
            < label for="email">Longitude</label>
            < input type="text" id="longitude" name="longitude" placeholder="-60.0014007" required="">
        < /div>
    < /div>
    < button type="submit" onclick="TestMarker();" class="btn"><img src="img/ico.ico"/>Localizar< /button>
< /form>
< script>
    var latitude = -14.6915082,
        longitude = -60.0014007,
        zoomap = 4,
        image = 'img/marcador.png',
        markmap = 0,
        map;
 
    function initMap() {
        var myLatLng = {lat: latitude, lng: longitude};
        map = new google.maps.Map(document.getElementById('map'), {
            zoom: zoomap,
            center: myLatLng
        });
    }
 
function TestMarker() {
    latitude = document.getElementById('latitude').value;
    longitude = document.getElementById('longitude').value;
    Busca = new google.maps.LatLng(latitude, longitude);
    markmap = 1,
    addMarker(Busca);
}
 
function addMarker(location) {
    marker = new google.maps.Marker({
        position: location,
        animation: google.maps.Animation.DROP,
        map: map,
        icon: image
    });            
}
</script>
<script async defer
src="https://maps.googleapis.com/maps/api/js?key=xxxxx_in=true&callback=initMap">
</script>