I use OziExplorer for the GPS overlays, and the cost is something like $75. It is well worth it, because of Ozi exporting WGS84 .SHP Files that can be use for vector overlays in GIS software like MicroDem.
Getting back to the Terrain Visualization: Rolls 4 & 5 of my album are looking down the fire road towards the lake at the spot where I marked "Heavy Trail Traffic". The free Digital Elevation Models do not have enough resolution to show the deep ravine running along the east side of the fire road, and the deer avoid this obstacle to pass by Cam #1. So, there are limitations. Also, the elevation model that I have posted is in "Reflectance" mode, and just about anything can be used as an overlay, including Satellite images or a topographical map. But, there are some real big limitations in that mode, like it takes all day for the computer to do the job.
The name of the software is "MicroDEM", and it's available free from one of the professors at the US Naval Academy. I posted the MicroDEM WebPage above in this thread. MicroDEM also goes by the name of "Terra Base II", and is available free from Fort Leonard Wood Engineering School. The Army version is older bug free software, but I prefer the latest version from the Naval Academy. I started using MicroDEM with Windows 3.1, and sort of grew up with it.
MicroDEM will handle GPS, but OziExplorer offers so much more that I paid the $75. The 2 red specks on my terrain visualization, where CAM 1 & 2 are located, are actual saved GPS Waypoints from my Garmin 12XL. They were loaded into OziExplorer, and exported as a <.SHP> file. Then MicroDEM imported this vector file as an overlay. The black line was generated inside of Ozi using a free Quadrangle Map, and I tracing a Garmin track to be exported as a <.SHP> file. The red lines are fire roads that are part of the county wide Tiger Census Bureau, and is available free at GIS Data Depot (posted above)