impedance is a grid attribute containing a resistance value for each cell.
startvalues contains the initial impedance values for the point set.
The impedance is calculated taken into account the length of each cell (with value 1 for each cell) and the grid cell impedance. The resulting values unit has a float32 or float64 value type, based on the value type of the impedance and startvalues arguments. The resulting domain unit is the domain unit of the impedance argument.
The griddist function is often used to calculate off road travel resistances, where e.g. the land use type and the slope have an important influence on the travel time/costs.
The values unit of the arguments impedance and startvalues must match.
The domain of the arguments destpoint_gridid and startvalues must match.