The final output for this project is in fact one step short of the desired result. Having achieved a friction surface which I believe accurately reflects the specified parameters, I was still unable to succesfully use IDIRISI's least cost analysis function to calculate an appropriate route.

Working on the assumption that PATHWAY will only count out along adjacent cells of LOWER value, I used the image calculator to reverse all pixel values on the friction layer (using the expression: -1*((image)-maxvalue), so that values decreased with distance from the trailhead. When this this did not work it became clear that the problem occured with the decision wizard, zooming into the image MCETRAIL (below) shows that there are gaps of zero value across the surface.These zeros prevent the least cost path from being claculated because it automatically encounters a local minimum. Attempts at correcting this with a mean or max filter, or an underlay-except-where-zero of a blank boolean image of ones also failed to enable PATHWAY.

In hindsight this is likely because MCE decision wizard the did not carry over all values from the inputs, or (more likely) the reprojection of the vegetaion type and road input images did not match the other layers.

IMAGE: pixelated_mcetrail

Having said this, the final suitability image does provide a good framework for NPS to look at the north east slope just below our chosen trail head for a new trailroute and hopefully justifies the exorbitant consultation fee we will be sending them.