A method of increasing accuracy of location determination of mobile devices within a location-based subgroup starts with server receiving location data and proximity information from each of the mobile devices. Location data received from first mobile device includes first mobile device's fixed location. Proximity information received from first mobile device includes an identification of mobile devices within a proximity sensitivity radius of first mobile device's location. Server forms subgroup of mobile devices based on proximity information from each of the mobile devices. Subgroup may include first mobile device and mobile devices that have provided proximity information that identifies first mobile device are being within the proximity sensitivity radiuses of the mobile devices, respectively. Server may then refine the fixed location of the first mobile device, which includes identifying an intersection of the proximity sensor sensitivity of each of the mobile devices that are in subgroup. Other embodiments are described.