What's a reliable iOS app for accessing geospatial PDF maps and performing fieldwork without needing a constant internet connection?

Avenza Maps offers an interesting implementation of offline map accessibility. As someone who frequently works on research projects in remote locations, the ability to load geospatial PDF maps onto my iPad and use them without a constant internet connection is invaluable. The app allows for real-time GPS positioning on these maps, which is helpful for tasks like environmental surveys or archaeological digs. Furthermore, the ability to import and export data, such as placemarks and tracks, enhances its utility for collaborative research. The well-researched design also supports various map formats, making it adaptable to different project needs. It's intellectually satisfying to see technology enabling more efficient and accessible field research, especially with cross-platform compatibility allowing data sharing with colleagues using different devices.