Lakes Frome, Callabonna, Blanche and Gregory are playa lakes on the eastern and northern sides of the Flinders Ranges, South Australia. Between 2007 and 2019 we surveyed key topographic features of the lakes, including shorelines, lake floors and the alluvial sills that separate the lakes with differential GPS (DGPS). We combine these observations with the analysis of a hybrid DEM that blends data from multiple sources. The lowest elevation of the Frome-Callabonna system based on the hybrid DEM is −8.33 m Australian Height Datum (AHD) at Lake Callabonna but −5.42 m AHD based on DGPS field data. Both values are considerably lower than previous estimates based on spot heights and contours. The DGPS data for Lake Callabonna support the Shuttle Radar Terrestrial Mission (SRTM) estimates of lake-floor elevations but with a mean difference of 1.7 m in elevation. There are larger differences in elevation between the hybrid DEM and the DGPS data for the floor of Lake Frome (mean difference