Path Distance algorithm

Discussion created by simam on Mar 20, 2012
Hi,
I have two questions regardin the algorithm which is used for calculating the cost_distance values in the 'Path Distance' tool. As it is described in its help page, cost-distance calculation follows the formula:

Cost-Distance = cost-surface*surface-distance*([friction a * Horizontal Factor a + Friction b* Horizontal Factor b]/2)* vertical factor
which is multiplied by 1.4 in case of diagonal movement from cell to cell.

1- what happens if we do not define any Vertical Factor in the tool? what is the default value which would be assigned to it?

when it comes to calculate the accumulated-cost it uses the following formula:

accumulated-cost-distnace= a1+ surface-distance*([friction b* Horizontal Factor b + Friction c* Horizontal Factor c]/2)* vertical factor, and my next question is :

2-why it doesn't use the "Cost-Surface" term in this step anymore? doesn't it really follow the same concep as the previous formula to calculate the cost of movement to proceed to the next cells or is there any other explanation for it?