The described technology is generally directed towards digital map truth maintenance. Map inputs shared among multiple users of a shared overlay map service can have a range of credibility, from not credible to highly credible. The disclosed digital map truth maintenance technologies can be used to enhance credibility of shared map inputs. Credibility values can be calculated for map inputs, based on any of multiple factors. Map inputs having sufficiently high credibility, such as a credibility value determined to be above a threshold value, can be shared among multiple mobile devices.