RF viewshed analysis taking into account ground type reflectivity

I have a project that we are conducting RF analysis coverage and need to take into account the reflectivity of the ground, the ground type is in Hawaii near 2 volcanoes with one of them last active in 1984. This ground type has played a part in the RF reflectivity in the past. Is there a way to add this capability into Global Mapper?
Comments
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com