Over the years I've acquired some GIS skills and there are a variety of free viewers/software that one can download.
The ones I find most useful have the ability to stack aerial photos, DRG (digital raster graphics or topo maps), and DEM's (digital elevation models), and then render those in 3D. One can make one or more layers transparent so he can simultaneously look through a topo map at an underlying photo or switch focus back to a single layer at a time. Very handy. One can spin or tilt the view to see the country from any angle or elevations. Some even have the ability to do fly overs.
It takes some computing/graphic card power to do that effectively with a couple hundred square miles of country at something like 1 square ft to a pixel, so one will not be doing those exercises with smart phones or pads.
Some of the same software can derive least effort pathways between selected points and those can be downloaded to ones GPS. It makes ones hikes considerably easier too distant points in rugged terrain.
Our party will spend several hours on such endeavors when taking on new country, and we save all the data to DVD's or external hard drives for our repeat areas. It greatly enhances our efficacy and strategies when working big country. We will also print off about a 3 by 4 ft hard copy of the aerial photo and hang that in the wall tent for on site planning.
All of these maps and images can be had for free over the web.
Last, here is a handy link for running down sites. If one is in the barber chair and happens to overhear a reference to something like "Dead Indian Springs" or "Coffee Pot Creek" he can go here and run down its precise location. Found quite a few secret spots with this method.
Locating secret spotsHappy trails,