Add two text inputs to your form.
Paste the code below into a html element. Adjust the item2_test_1 and item4_test_1 to the ID's of your actual inputs.

<script>
navigator.geolocation.getCurrentPosition(GetLocation);
function GetLocation(location) {
document.getElementById('item2_text_1').value=location.coords.latitude;
document.getElementById('item4_text_1').value=location.coords.longitude;
}</script>