AYD and EYD are in slope distance. For ground based skidding, to account for slope and circuity of skid, it is usual to multiply map distance by 1.2 to estimate acutal distance across the ground surface. For cable units, use the actual pathway slope to obtain the conversion from map distance to slope distance.

The AYD location for any unit is analagous to the center of mass of the timber on the unit. An assumption can be made that all MBF on the cutting unit is hauled from this point and, hence, simplified cost and production computation estimates are possible.