Tom,
You're so right about it being difficult to know where you are going or for that matter, to know exactly where you are in thick vegetation when on the ground.
Being the tech-geek that I am, it is possible to use pro-grade submeter gps, WAAS capable so you have 'realtime' positioning, on the ground...into that load the site aerial and topo, use the 'line feature' in the mapping software, it like leaving a trail of breadcrumbs, and simply record your position/movement across the site.
You can see yourself on the ground, on the handheld PDA, like Mike Nuzzo says "I'm a giant pencil" as you go, make numerous routes, load that into you PC and voila...you have each day's recon study and evaluate.
Also possible to view alternate routing on the same basemap.
Maybe better to use a ruggedized tablet PC for bigger screen...my tired old eyes sure appreciate it.
Frankly, some gps setups are so ergonomic, you can wear them and not even know you have it on you. Antenna in hat on your head, small lightweight gps in your pocket or vest.
Just a thought for what's it is worth.