Cloud Detection
- Author: J.Spitzm_ller, O.Conrad (c) 2023
- Menu: Imagery | Feature Extraction
Description
This tool implements pass one of the Function of mask (Fmask) algorithm for cloud and cloud shadow detection in Landsat imagery. Landsat Top of Atmosphere (TOA) reflectance and Brightness Temperature (BT) are used as input.
Alternatively you can choose the scene-average automated cloud-cover assessment (ACCA) algorithm as proposed by Irish (2000) and Irish et al. (2006).
This tool can optionally pass the cloud mask to the "Cloud Shadow Detection" tool as well.
References
- Irish, R.R. (2000): Landsat 7 Automatic Cloud Cover Assessment. In: Shen, S.S., Descour, M.R. [Eds.]: Algorithms for Multispectral, Hyperspectral, and Ultraspectral Imagery VI. Proceedings of SPIE, 4049: 348-355. doi:10.1117/12.410358.
- Irish, R.R., Barker, J.L., Goward, S.N., Arvidson, T. (2006): Characterization of the Landsat-7 ETM+ Automated Cloud-Cover Assessment (ACCA) Algorithm.. Photogrammetric Engineering and Remote Sensing vol. 72(10): 1179-1188. doi:10.14358/PERS.72.10.1179.
- Tizado, E.J. (2010): GRASS GIS i.landsat.acca. E.J. Tizado's implementation of the ACCA algorithm as proposed by Irish (2000), Irish et al. (2006). Source Code.
- Zhu, Z., Wang, S., Woodcock, C.E. (2015): Improvement and expansion of the Fmask algorithm: cloud, cloud shadow, and snow detection for Landsats 4-7, 8, and Sentinel 2 images. Remote Sensing of Environment 159, 269-277. doi:10.1016/j.rse.2014.12.014.
- Zhu, Z., Woodcock, C.E. (2012): Object-based cloud and cloud shadow detection in Landsat imagery. Remote Sensing of Environment 118, 83-94. doi:10.1016/j.rse.2011.10.028.
Parameters
| | Name | Type | Identifier | Description | Constraints |
|---|
| Input | Blue | grid, input | BAND_BLUE | - | - |
| Green | grid, input | BAND_GREEN | - | - |
| Red | grid, input | BAND_RED | - | - |
| Near Infrared | grid, input | BAND_NIR | - | - |
| Shortwave Infrared 1 | grid, input | BAND_SWIR1 | - | - |
| Shortwave Infrared 2 | grid, input | BAND_SWIR2 | - | - |
| Thermal | grid, input, optional | BAND_THERMAL | - | - |
| Cirrus | grid, input, optional | BAND_CIRRUS | - | - |
| Output | Clouds | grid, output | CLOUDS | - | - |
| Options | Grid System | grid system | PARAMETERS_GRID_SYSTEM | - | - |
| Grid System | grid system | BANDS_SWIR | - | - |
| Grid System | grid system | BANDS_THERMAL | - | - |
| Grid System | grid system | BANDS_CIRRUS | - | - |
| Unit | choice | THERMAL_UNIT | - | Available Choices:
[0] Kelvin
[1] Celsius
Default: 0 |
| Algorithm | choice | ALGORITHM | - | Available Choices:
[0] Fmask
[1] ACCA
Default: 0 |
| SWIR/Thermal Threshold | floating point number | ACCA_B56C | Threshold for SWIR/Thermal Composite (step 6). | Default: 225.000000 |
| Desert Detection Threshold | floating point number | ACCA_B45R | Threshold for desert detection (step 10, NIR/SWIR Ratio). | Default: 1.000000 |
| Temperature Histogram | integer number | ACCA_HIST_N | Number of classes in the cloud temperature histogram. | Minimum: 10
Default: 100 |
| Cloud Signature | boolean | ACCA_CSIG | Always use cloud signature (step 14). | Default: 1 |
| Cloud Differentiation | boolean | ACCA_PASS2 | Differentiate between warm (not ambiguous) and cold clouds. | Default: 0 |
| Shadows | boolean | ACCA_SHADOW | Include a category for cloud shadows. | Default: 0 |
| Shadow Detection | boolean | SHADOWS | Run cloud shadow detection tool with standard settings. | Default: 0 |
| Sun's Azimuth | floating point number | SUN_AZIMUTH | Direction of sun clockwise from North [degree]. | Minimum: 0.000000
Maximum: 360.000000
Default: -180.000000 |
| Sun's Height | floating point number | SUN_HEIGHT | Height of sun above horizon [degree]. | Minimum: 0.000000
Maximum: 90.000000
Default: 45.000000 |
Command Line
Usage: saga_cmd imagery_tools 20 [-CLOUDS ] [-BAND_BLUE ] [-BAND_GREEN ] [-BAND_RED ] [-BAND_NIR ] [-BAND_SWIR1 ] [-BAND_SWIR2 ] [-BAND_THERMAL ] [-BAND_CIRRUS ] [-THERMAL_UNIT ] [-ALGORITHM ] [-ACCA_B56C ] [-ACCA_B45R ] [-ACCA_HIST_N ] [-ACCA_CSIG ] [-ACCA_PASS2 ] [-ACCA_SHADOW ] [-SHADOWS ] [-SUN_AZIMUTH ] [-SUN_HEIGHT ]
-CLOUDS: Clouds
grid, output
-BAND_BLUE: Blue
grid, input
-BAND_GREEN: Green
grid, input
-BAND_RED: Red
grid, input
-BAND_NIR: Near Infrared
grid, input
-BAND_SWIR1: Shortwave Infrared 1
grid, input
-BAND_SWIR2: Shortwave Infrared 2
grid, input
-BAND_THERMAL: Thermal
grid, input, optional
-BAND_CIRRUS: Cirrus
grid, input, optional
-THERMAL_UNIT: Unit
choice
Available Choices:
[0] Kelvin
[1] Celsius
Default: 0
-ALGORITHM: Algorithm
choice
Available Choices:
[0] Fmask
[1] ACCA
Default: 0
-ACCA_B56C: SWIR/Thermal Threshold
floating point number
Default: 225.000000
-ACCA_B45R: Desert Detection Threshold
floating point number
Default: 1.000000
-ACCA_HIST_N: Temperature Histogram
integer number
Minimum: 10
Default: 100
-ACCA_CSIG: Cloud Signature
boolean
Default: 1
-ACCA_PASS2: Cloud Differentiation
boolean
Default: 0
-ACCA_SHADOW: Shadows
boolean
Default: 0
-SHADOWS: Shadow Detection
boolean
Default: 0
-SUN_AZIMUTH: Sun's Azimuth
floating point number
Minimum: 0.000000
Maximum: 360.000000
Default: -180.000000
-SUN_HEIGHT: Sun's Height
floating point number
Minimum: 0.000000
Maximum: 90.000000
Default: 45.000000