Pharos: a mobile GIS application for network assessment and ground-truth mapping to support mHealth study design in low-resource settings.

Mobile health (mHealth) is a promising tool for improving healthcare access, particularly in low-resource settings. However, limited mobile accessibility and poor connectivity remain significant barriers to implementing mHealth interventions in these regions. To address these challenges and support the development and scalability of mHealth studies, we developed Pharos, a mobile GIS application designed to assess network coverage and facilitate ground-truth mapping. Pharos autonomously measures spatiotemporal variations in mobile network signal strength and enables precise mapping of critical landmarks and environmental features. We deployed Pharos in a four-county region along the shores of Lake Victoria in Western Kenya as part of a preparatory phase for a large-scale mHealth study focused on schistosomiasis control. Over six months and 10,000 km2, Pharos collected high- resolution data on network performance and landmark locations, generating a comprehensive dataset that links network availability with environmental features. These results provide essential insights for planning and implementing mHealth interventions in low-resource settings, with potential applications in infectious disease surveillance and other global health initiatives.