The Auto Flat / Pit Removal tool automates the removal of flat and pit pixels from the DEM by sequentially applying the filling algorithm and breaching algorithm. The tool is intended to improve the ease of application of the flat and pit removal algorithms with minimal intervention from the user. The Auto Flat / Pit Removal tool has been found to provide acceptable treatment of flat and pit pixels in most circumstances.
The Auto Flat / Pit Removal tool operates by firstly applying the filling algorithm to treat flattened hill crests etc. The filling algorithm terminates when one of the following criteria is satisfied (set in Project Options form):
1. A maximum number of iterations is met (default 50); or
2. The percentage reduction in pit / flat pixels between successive iterations is less than a specified amount (default 5%).
The termination criteria for the filling algorithm can be altered on the CatchmentSIM Drop Down >> Project Options | Flat and Pit Removal page if required.
Next the breaching algorithm is applied to remove any flat and pit pixels that remain following application of the filling algorithm. The breaching algorithm is applied to the entire DEM and will generally resolve all outstanding flat and pit pixels provided a minimum downslope gradient can be met.
Further information on the filling algorithm and breaching algorithm is provided in the following sections.
