Fine-scale tracking of animal movement is important to understand the proximate mechanisms of animal behaviour. While GPS tracking is an excellent tool for measuring animal movement, it often causes a trade-off between tag weight, cost and lifespan that limits its application to relatively large individuals, a small number of individuals or short tracking durations, respectively. The reverse-GPS system, ATLAS, uses lighter, cheaper tags that last long periods of time at the similar sampling frequencies to GPS. ATLAS provides a regional-scale alternative to global GPS-based tracking with which hundreds of relatively small-bodied species can be tracked simultaneously for long periods of time. Here, we test the accuracy and precision of an ATLAS system, using concurrent GPS measurements as a reference. To measure accuracy, we calculated the distance between ATLAS and GPS location estimates for a route (mobile test) and 16 fixed locations (stationary test) on the Griend mudflat, the Netherlands. This location is the focus of a large-scale ATLAS system in the Wadden Sea consisting of 26 receivers and covering 1326 km2 of intertidal region, with almost no physical obstacles for radio signals. ATLAS-derived location estimates differed on average 4.2 m from GPS-estimated stationary test sites and 5.7 m from GPS tracks taken whilst moving between them. Signals that were collected by more receiver stations were more accurate, although even 3-receiver localisations were comparable with GPS localisations (~10 m difference). Higher receiver stations detected the tag at further distances. In conclusion, ATLAS provides an alternative to GPS for regional-scale animal movement studies by providing movement data of comparable spatial accuracy. The growing use of the ATLAS systems motivates further refinement of best-practice application, such as considering the height of receivers, their spatial arrangement, density and the movement mode of the study species (e.g., ground-dwelling or flying).