Here's my problem: I have a network of trails between locations scattered across the eastern US (think hiking trails, on foot, not vehicular travel).
I would like to calculate on-foot travel time (time unit doesn't matter-- seconds, minutes, hours, etc.) between individual locations using exclusively trails within that network.
I have a friction surface calculated from a base DEM (using Tobler's hiking function).
I may include waterways (I have this data from the NHD).
I know how to build a basic least-cost / cost-distance model, and how to set friction values for "desired" routes lower than the surrounding terrain.
What I don't know at this point is: How can I extract travel times from these data? Is that even possible within this type of calculation or from the products of such a model?
Note: I know that there is at least one "canned" solution that does something a little like this (the NPS has its "travel time cost surface model" toolbox).
The problem with the TTCSM is that it looks outward from a central point in all directions, based on a given time, and terminates the calculation once that "time" is reached in all directions.
I'm also not a fan of black box solutions, which the TTCSM definitely is. It works, but for what I'm doing, I need to know what's happening under the hood.