<apex:page standardController="Project__c" id="page" docType="html-5.0">
<p><button onclick="geoFindMe()">Show my location</button></p>
<p id="out"></p>
<script>
  geoFindMe();
  callSave();
  reload();


function geoFindMe() {
  var output = document.getElementById("out");

  if (!navigator.geolocation){
    output.innerHTML = "<p>Geolocation is not supported by your browser</p>";
    return;
  }

  function success(position) {
    var latitude  = position.coords.latitude;
    var longitude = position.coords.longitude;

    document.getElementById('page:form:lati').value = latitude.toString().replace(".",",")  ;
    document.getElementById('page:form:long').value = longitude.toString().replace(".",",")  ; 


   
  };

  function error() {
    output.innerHTML = "Unable to retrieve your location";
  };

  navigator.geolocation.getCurrentPosition(success, error);
}
</script>

<script>
function  reload(){
   sforce.one.back(true);
}
</script>

<apex:form id="form">


latitude :<apex:inputField id="lati"  value="{!Project__c.l__c}" /> 
longitude :<apex:inputField id="long" value="{!Project__c.ll__c}" />

   <apex:commandButton action="{!save}"  value="Save" oncomplete="reload()"/>
      
   <apex:actionFunction name="callSave" action="{!save}" />           
</apex:form>

</apex:page>