Tool Name	Multi Direction Lee Filter
Tool ID	3
Library ID	grid_filter
Version	1.0
Author(s)	A.Ringeler (c) 2003

Description

The tool searches for the minimum variance within 16 directions and applies a Lee Filter in the direction of minimum variance. The filter is edge-preserving and can be used to remove speckle noise from SAR images or to smooth DTMs. Applied to DTMs, this filter will preserve slope breaks and narrow valleys.
For more details, please refer to the references.

References

Lee, J.S. (1980): Digital image enhancement and noise filtering by use of local statistics. IEEE Transactions on Pattern Analysis and Machine Intelligence, PAMI-2: 165-168.

Lee, J.S., Papathanassiou, K.P., Ainsworth, T.L., Grunes, M.R., Reigber, A. (1998): A New Technique for Noise Filtering of SAR Interferometric Phase Images. IEEE Transactions on Geosciences and Remote Sensing 36(5): 1456-1465.

Selige, T., BÃ¶hner, J., Ringeler, A. (2006): Processing of SRTM X-SAR Data to correct interferometric elevation models for land surface process applications. In: BÃ¶hner, J., McCloy, K.R., Strobl, J. [Eds.]: SAGA - Analysis and Modelling Applications. GÃ¶ttinger Geographische Abhandlungen, Vol. 115: 97-104. http://downloads.sourceforge.net/saga-gis/gga115_09.pdf

Parameters

Name	Type	Identifier	Description	Constraints
Input
Grid	grid, input	INPUT
Output
Filtered Grid	grid, output	RESULT
Minimum Standard Deviation	grid, output, optional	STDDEV
Direction of Minimum Standard Deviation	grid, output, optional	DIR
Options
Estimated Noise (absolute)	floating point number	NOISE_ABS	Estimated noise in units of input data	Minimum: 0.000000 Default: 1.000000
Estimated Noise (relative)	floating point number	NOISE_REL	Estimated noise relative to mean standard deviation	Minimum: 0.000000 Default: 1.000000
Weighted	boolean	WEIGHTED		Default: 1
Method	choice	METHOD		Available Choices: [0] noise variance given as absolute value [1] noise variance given relative to mean standard deviation [2] original calculation (Ringeler) Default: 1