Abstract: Low-cost GNSS receiver modules are widely used in lightweight and small unmanned aerial vehicle (UAV)-based surveying and remote sensing applications due to their centimeter-level real time kinematic (RTK) / post processed kinematic (PPK) positioning accuracy. To evaluate the RTK/PPK positioning potential of low-cost receiver modules mounted on rotorcraft UAVs, an onboard RTK experiment is conducted using a quadrotor UAV. The positioning potential of the low-cost module is assessed by comparing their RTK/PPK results with those from a geodetic-grade multi-frequency receiver. The results show that the root mean square error (RMSE) of the horizontal and vertical differences between the RTK positioning results of the low-cost receiver module and the dual-frequency geodetic receiver are 5.4 mm and 16.6 mm, respectively. For PPK positioning, the horizontal and vertical RMSE are 2.5 mm and 4.7 mm, respectively. These findings provide practical evidence supporting the use of low-cost receiver modules in high-precision mapping applications for low-altitude UAVs.