GPR Viewer from www.gpr-archaeology.com is one of the best tools for viewing GPR data. This is a FREE tool made by Lawrence B. Conyers. When compared with options like RADAN 7 offered by GSSI it may be lacking features, but when you are talking free vs $4000 per computer it's an amazing solution. I have used GprViewer many times for large and small projects even on occasion over RADAN 7 of with we have a full copy. When I am having issues interpreting the data I am looking at throwing some passes in GprViewer and taking a better look has saved me more than a few times. One of my personal favorite features is how it handles gain. You can vary the gain at different depths and get a clearer picture of what is going on. I would love to see this ported to Android or IOS for use on a tablet, but being as this is a free program that would be a value option at several hundred dollars you really can't complain.