I would like to know in order to use this query through REST API....do we need to call salesforce support and enable it.

It was actually in pilot mode and available for Developer Edition and Sandboxes and not for Production.

What actually is pilot feature in Salesforce???

Please clarify!!!!!!

SELECT caseNumber, location__latitude__s, location__longitude__s FROM Case
WHERE DISTANCE(location__c, GEOLOCATION(<latitude and longitude coordinates of mobile device>), 'mi') <= 10