making first ArmA 3 map need advice

I have purchased Global Mapper and have obtained some DEM and GeoTIFF data on an Atlantic Island I want to recreate in ArmA 3. I figured that creating a terrain from existing real world data would be easier. Many people suggest using L3DT for your layers but I am curious about what all files I can create from Global Mapper. I am wondering if it is possible to skip L3DT and just use Global Mapper to supply all the necessary files for Terrain Builder. If so, what files and file types do I need to export from Global Mapper and what types of data do I need to download?

Thanks.