Systems and methods are provided for generating a reference location data set, such as a reference longitude and latitude point, for each of a plurality of point addresses. A reference location data set can be determined for a point address based on a history of prior geocode samples, such as GPS readings, that have been obtained using a portable computing device during a prior delivery to or pickup from the point address. A location data service collects such geocode samples and processes the samples to generate a reference location data set, such as a reference longitude and latitude and a zone of confidence around the reference longitude and latitude, for each unique point address. To determine whether an item is being delivered to a wrong address, current location data obtained during a delivery can be compared against the reference location data generated by the location data service for the delivery address.