The mobile device should make a REST Apex inbound call to meet the requirement. A REST Apex inbound call allows the mobile device to invoke custom Apex logic on Salesforce using a RESTful interface. The Apex logiccan then access the geolocation field using the user’s OAuth token and update it with the GPS coordinates from the mobile device. The geolocation field is secured with Field Level Security, so the user can view the value without changing it. A SOAP API inbound call or a REST API inbound call would not be able to access the custom geolocation field, as they are not supported by the standard Salesforce objects and fields. Reference: Salesforce Integration Architecture Designer Resource Guide, page 20