In some implementations, a server device can improve Wi-Fi based location availability for sparse signal locations by augmenting Wi-Fi access point location data with additional Wi-Fi scan data that was collected near the sparse signal locations. The server can receive Wi-Fi access point scans from client devices, determine the locations of the Wi-Fi access points, and generate Wi-Fi access point tiles that include data describing the locations of access points in the geographic areas corresponding to the Wi-Fi access point tiles. After the tiles are generated, the server device can augment the access point tiles by inserting additional Wi-Fi access point scan information into the access point tiles near identified sparse signal locations. The server device can deliver the augmented access point tile data to a client device. The client device can determine the current location of the client device based on the augmented access point tile data.