Hi Hitesh,

here is the code.

Thanks
Reshmi

Apex Class

public with sharing class 
FindNearbyController{
    public List<Map<String,Double>> locations { get; private set; }    
 public String currentPosition {          
get {             
if (String.isBlank(currentPosition)) {                 
currentPosition = '37.77493,-122.419416'; // San Francisco             }             
return currentPosition;         }         
set;      }          
public Boolean resultsAvailable {         
get {             if(locations == Null) {                 
return false;             }             
return true;         }     }          
public PageReference findNearby() {         
String lat, lon;         
// FRAGILE: You'll want a better lat/long parsing routine         
// Format: "<latitude>,<longitude>" (must have comma, but only one comma)         
List<String> latlon = currentPosition.split(',');         
lat = latlon[0].trim();         
lon = latlon[1].trim();         
// SOQL query to get the nearest Contacts            
// SOQL query to get the nearest Contacts
           String queryString =
           'SELECT Id, Name, MailingStreet, MailingCity, MailingState, Phone, Location__longitude__s, Location__latitude__s ' +
           'FROM Contact ' +
           'WHERE DISTANCE(Location__c, GEOLOCATION('+lat+','+lon+'), \'mi\') < 20 ' +
           'ORDER BY DISTANCE(Location__c, GEOLOCATION('+lat+','+lon+'), \'mi\') ' +
           'LIMIT 10';
        System.Debug('>>>> the value of queryString is ' + queryString);
        // Run the query
 
       List <Contact> contacts = database.query(queryString);
        if(contacts.size() > 0 ) {
            // Convert to locations that can be mapped
            locations = new List<Map<String,Double>>();
            for (Contact con : contacts) {
                locations.add( new Map<String,Double>{
                        'latitude' => con.Location__latitude__s,
                        'longitude' => con.Location__longitude__s
                    }
                );
            }
        }
        else {
            System.debug('No results. Query: ' + queryString);
        }
                
        return null;
    }
}

VF Code
<apex:page controller="FindNearbyController" docType="html-5.0" >

    <!-- JavaScript to get the user's current location, and pre-fill the currentPosition form field. -->
    <script type="text/javascript">
        // Get location, fill in search field
        function setUserLocation() {
            if (navigator.geolocation) {
                navigator.geolocation.getCurrentPosition(function(loc){
                    var latlon = loc.coords.latitude + "," + loc.coords.longitude;
                    var el = document.querySelector("input.currentPosition");
                    el.value = latlon;
                });
            }
        }
        // Only set the user location once the page is ready
        var readyStateCheckInterval = setInterval(function() {
            if (document.readyState === "interactive") {
                clearInterval(readyStateCheckInterval);
                setUserLocation();
            }
        }, 10);
    </script>
   <apex:pageBlock >
        <!-- Form field to send currentPosition in request. You can make it an <apex:inputHidden> field to hide it. -->
        <apex:pageBlockSection >
            <apex:form >
                <apex:outputLabel for="currentPosition">Find Nearby</apex:outputLabel>
                <apex:input size="30"
                     html-placeholder="Attempting to obtain your position..."
                     id="currentPosition" styleClass="currentPosition"
                     value="{!currentPosition}" />
                <apex:commandButton action="{!findNearby}" value="Go!"/>
            </apex:form>
        </apex:pageBlockSection>
        
        <!-- Map of the results -->
        <apex:pageBlockSection rendered="{!resultsAvailable}" title="Locations">
            <apex:map width="600px" height="400px">
            <!-- Add markers for contacts -->
                <apex:repeat value="{!locations}" var="pos">
                    <apex:mapMarker position="{!pos}"/>
                    <!-- Add info window with contact details -->
                    <apex:mapInfoWindow>
                    <apex:outputPanel layout="block" style="font-weight: bold;">
                    <apex:repeat value="{!contacts}" var="con">
                        <apex:outputText>{!con.Name }</apex:outputText>
                     </apex:repeat>
                     </apex:outputPanel>
                    </apex:mapInfoWindow>
                 </apex:repeat>
            </apex:map>
        </apex:pageBlockSection>
    </apex:pageBlock>
</apex:page>