Direct neighbourhood functions: derivatives of elevation

Calculate derivatives of an elevation model over a 3 x 3 cell window

Example 1:

Result = slope(expression)

expression: digital elevation model

Example 2:

Result = lddcreate(expression, outflowdepth, corevolume, corearea, catchmentprecipitation)

expression: digitial elevation model

other arguments: pit removal options (see manual and practical)

Result: local drain direction map, each cell has a direction of flow to one of its neighbours