NRH imaging of the Type III radio burst sources at 150 MHz, overlaid on an AIA 171 Å image, together with a PFSS derived from GONG. The 150 MHz sources, consistently observed at approximately ∼0.25 R_⊙, align with the multilateration results. The radio emission is associated with a B-class flare, as shown in Fig. A.2. Additionally, the PFSS shows a large group of open magnetic field lines at the 150 MHz location, which is consistent with the Parker spiral derived from the multilateration results.