Tool Multi Direction Lee Filter
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., Böhner, J., Ringeler, A. (2006): Processing of SRTM X-SAR Data to correct interferometric elevation models for land surface process applications. In: Böhner, J., McCloy, K.R., Strobl, J. [Eds.]: SAGA - Analysis and Modelling Applications. Göttinger Geographische Abhandlungen, Vol. 115: 97-104. http://downloads.sourceforge.net/saga-gis/gga115_09.pdf.
- Author: A.Ringeler (c) 2003
- Menu: Grid|Filter
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 | Grid System | Grid system | PARAMETERS_GRID_SYSTEM | - | - |
| Estimated Noise (absolute) | Floating point | NOISE_ABS | Estimated noise in units of input data | Default: 1.000000 |
| Estimated Noise (relative) | Floating point | NOISE_REL | Estimated noise relative to mean standard deviation | 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 |
| (*) optional |
Command-line
Usage: saga_cmd grid_filter 3 [-INPUT <str>] [-RESULT <str>] [-STDDEV <str>] [-DIR <str>] [-NOISE_ABS <double>] [-NOISE_REL <double>] [-WEIGHTED <str>] [-METHOD <str>]
-INPUT:<str> Grid
Grid, input
-RESULT:<str> Filtered Grid
Grid, output
-STDDEV:<str> Minimum Standard Deviation
Grid, output, optional
-DIR:<str> Direction of Minimum Standard Deviation
Grid, output, optional
-NOISE_ABS:<double> Estimated Noise (absolute)
Floating point
Default: 1.000000
-NOISE_REL:<double> Estimated Noise (relative)
Floating point
Default: 1.000000
-WEIGHTED:<str> Weighted
Boolean
Default: 1
-METHOD:<str> Method
Choice
Available Choices:
[0] noise variance given as absolute value
[1] noise variance given relative to mean standard deviation
[2] original calculation (Ringeler)
Default: 1