Identify Flat Areas

Description

Leverage geomorphon landform classification to identify flat areas in the elevation raster. Tool performs several operations:

1. Generate landform classification.
2. Smooth landforms using majority filter and boundary clean operators.
3. Create initial flat areas based on user provided categories.
4. Remove areas smaller than user provided area threshold.
5. Create raster and vector representation of the final polygons.
   1. Calculate "Compactness" attribute for the polygons.

The result of the tool is a landform raster, flat area raster (Value = 1) and flat area polygon with attribute "Compactness" computed. Compactness is a measure of roundness of a shape. It is calculated as (perimeter**2)/(4*Pi*area). Value is equal to 1 for a circle and is a large number for shapes with complex, irregular boundaries.

If the data are not in projected coordinate system, minimal flat area unit conversion will not be performed, and the area threshold will be interpreted as number of cells.

While the intent of the tool is extraction of flat areas, any category of landforms can be extracted by providing single or a list of landforms to extract.

The results of this tool can be used for DEM hydro-conditioning (e.g., "Burn Flat Polygons into DEM").

Usage

Parameters

Parameter Name	Type	Direction	Data Type	Dialog Reference
Input DEM Raster	Required	Input	Raster Layer	Input elevation raster.
Flat Terrain Angle Threshold	Required	Input	Double	Geomorphon parameter. The angle threshold (in degrees) below which the target cell will be classified as flat. The default value is 1 degree. Specifying a larger value than the default is recommended for low resolution DEMs.
Search Distance	Required	Input	Double	Geomorphon parameter. The distance away from the target cell that defines the radius of the area that will be used to identify the geomorphon pattern. Measured in cells. The default value is 10. Use a search distance value that matches the type and size of the landforms that you want to classify.
Skip Distance	Required	Input	Double	Geomorphon parameter. The distance away from the target cell where the analysis area starts. Measured in cells. Neighboring cells that fall within this distance will be skipped and won't contribute to identification of the geomorphon pattern. The classification of each individual cell is determined by assessing the neighboring cells within the skip distance from the target cell center.
Flat Landform List	Required	Input	Multiple Value	List of landforms to include in raster extraction. One or more forms can be selected.
Minimum Flat Area Threshold	Required	Input	Areal Unit	Area that defines minimum contiguous polygons that will be saved. If "Unknow" units are selected, the tool will skip unit conversion and will treat the input number as number of cells.
Output Landform Raster	Required	Output	Raster Layer	The output classified landforms raster. The output is of integer type. Each value corresponds to a specific landform type: Flat - cell value 1, Peak - cell value 2, Ridge - cell value 3, Shoulder - cell value 4, Spur - cell value 5, Slope - cell value 6, Hollow - cell value 7, Footslope - cell value 8, Valley - cell value 9, Pit - cell value 10.
Output Flat Area Raster	Required	Output	Raster Layer	Output flat area raster (VALUE = 1).
Output Flat Area Polygon	Required	Output	Feature Layer	Output flat area polygon. It has field "Compactness" calculated as (perimeter**2)/(4*Pi*area).