FATMAP is described as 'Outdoor adventure platform with high-resolution 3D terrain maps, curated guides, offline downloads, live conditions, overlays, route planning, and mobile support' and is a GPS Navigation service in the travel & location category. There are more than 10 alternatives to FATMAP for a variety of platforms, including Android, iPhone, Android Tablet, iPad and Web-based apps. The best FATMAP alternative is CoMaps, which is both free and Open Source. Other great apps like FATMAP are Organic Maps, Google Earth, OsmAnd and Transportr.
it's the most similar application now that fatmap as been discontinued