The basaltic effusive eruption at Mt. Fagradalsfjall began on March 19, 2021, ending a 781-year hiatus on Reykjanes Peninsula, Iceland. By late September 2021, 32 near real-time photogrammetric surveys were completed using satellite and airborne images, usually processed within 3–6 hours. The results provide unprecedented temporal data sets of lava volume, thickness, and effusion rate. This enabled rapid assessment of eruption evolution and hazards to populated areas, important infrastructure, and tourist centers. The mean lava thickness exceeds 30 m, covers 4.8 km² and has a bulk volume of 150 ± 3 × 10⁶ m³. The March–September mean effusion rate is 9.5 ± 0.2 m³/s, ranging between 1–8 m³/s in March–April and increasing to 9–13 m³/s in May–September. This is uncommon for recent Icelandic eruptions, where the highest discharge usually occurs in the opening phase.