[GRASS-dev] GSoC 2018 final report week 13 - GRASS GIS module for Sentinel-2 cloud and shadow detection

Roberta Fagandini robifagandini at gmail.com
Tue Aug 14 02:48:03 PDT 2018


Thank you Moritz for your support!!

Roberta

2018-08-13 12:06 GMT+02:00 Moritz Lennert <mlennert at club.worldonline.be>:

> Great work, Roberta !
>
> Thanks for these two very useful modules !
>
>
> Moritz
>
> On 13/08/18 10:20, Roberta Fagandini wrote:
>
>> Hi all!
>> I'm Roberta Fagandini and this is the final report of my GSoC project.
>>
>> The title of the project is "GRASS GIS module for Sentinel-2 cloud and
>> shadow detection". It adds new tools for the processing of Sentinel 2
>> images to GRASS GIS software (Organization: OSGeo).
>>
>> *Abstract:*
>> Optical sensors are unable to penetrate clouds leading to related
>> anomalous reflectance values. Unlike Landsat images, Sentinel 2 datasets do
>> not include thermal and Quality Assessment bands that simplify the
>> detection of clouds avoiding erroneous classification. At the same time,
>> also clouds shadows on the ground lead to anomalous reflectance values
>> which have to be taken into account during the image processing.
>> The project creates a specific module for GRASS GIS application
>> (i.sentinel.mask) which implements an automatic procedure for clouds and
>> shadows detection for Sentinel 2 images. The procedure is based on an
>> algorithm, developed within my PhD research, which allows to automatically
>> identify clouds and their shadows applying some rules on reflectance values
>> (values thresholds, comparisons between bands, etc.). These have been
>> defined starting from rules found in literature and conveniently refined.
>> In order to increase the accuracy of the final results, a control check is
>> implemented. Clouds and shadows are spatially intersected in order to
>> remove misclassified areas. The final outputs are two different vector maps
>> (OGR standard formats), one for clouds and one for shadows.
>> To run i.sentinel.mask, the bands of the desired Sentinel 2 images have
>> to be imported and the atmospheric correction has to be applied.
>> In order to make the data preparation easier, another GRASS
>> GISaddonmodule has been developed within the GSoC project.
>> i.sentinel.preprocis a module for the preprocessing of Sentinel 2 images
>> (Level-1C Single Tile product) which wraps the import and the atmospheric
>> correction using respectively two existing GRASS GIS modules,
>> i.sentinel.import and i.atcorr.
>>
>> *The state of the art before the project:*
>> Before this GSoC 2018 project, no modules for the detection of clouds and
>> shadows were available for Sentinel 2 images. Only a specific module for
>> Landsat automatic cloud coverage assessment was available within GRASS GIS
>> (i.landsat.acca) while regarding shadows, no specific module was available.
>> Moreover, performing the atmospheric correction was a bit complicated
>> especially for unexperiencedusers who have to process one band at a time
>> and provide all input parameters manually.
>>
>> *The added value that the project brought to GRASS GIS:*
>> Now a specific module for clouds and shadows detection,
>> i.sentinel.mask,is available in GRASS GIS.
>> Moreover, i.sentinel.preprocprovides a simplified module which allows
>> importing images and performing the atmospheric correction avoiding users
>> to supply all the required input parameters manually. The module should
>> help users in preparing data to use as input for i.sentinel.mask. In fact,
>> it makes especially the atmospheric correction procedure easier and faster
>> because it allows performing atmospheric correction of all bands of a
>> Sentinel 2 scene with a single process and it retrieves most of the
>> required input parameters from the image itself. Moreover, one of the
>> possible output of i.sentinel.preprocis a text file to be used as input for
>> i.sentinel.mask.
>>
>> *Follow up:*
>> Both i.sentinel.mask and i.sentinel.preprocare complete and working
>> modules which can be easily installed with g.extension from the official
>> GRASS GIS SVN repository.
>> Obviously, they can be improved therefore the next steps could be:
>>
>>   * Implementation of other existing algorithms of clouds and shadows
>>     detection (i.sentinel.mask)
>>   * Implementation of a new download procedure avoiding dependencies
>>     (i.sentinel.preproc)
>>   * Integration of the Topographic Correction (i.sentinel.preproc)
>>
>> NOTE: Implementation of other existing algorithms of clouds and shadows
>> detection was one of the possible goals of the GSoC project but the
>> codingand debuggingof some parts of the twoaddonsrequired more time than
>> expected.
>>
>> *Permanent links:*
>> *
>> *
>> /Code developed during the GSoC coding period: /
>> https://github.com/RobiFag/GRASS_clouds_and_shadows <
>> https://github.com/RobiFag/GRASS_clouds_and_shadows>
>>
>> /Codes on the official GRASS GIS SVN repository:/
>> https://trac.osgeo.org/grass/browser/grass-addons/grass7/ima
>> gery/i.sentinel.mask <https://trac.osgeo.org/grass/
>> browser/grass-addons/grass7/imagery/i.sentinel.mask>
>> https://trac.osgeo.org/grass/browser/grass-addons/grass7/ima
>> gery/i.sentinel.preproc <https://trac.osgeo.org/grass/
>> browser/grass-addons/grass7/imagery/i.sentinel.preproc>
>>
>> /Documentation:/
>> https://grass.osgeo.org/grass74/manuals/addons/i.sentinel.mask.html <
>> https://grass.osgeo.org/grass74/manuals/addons/i.sentinel.mask.html>
>> https://grass.osgeo.org/grass74/manuals/addons/i.sentinel.preproc.html <
>> https://grass.osgeo.org/grass74/manuals/addons/i.sentinel.preproc.html>
>>
>> /Weekly reports: /
>> https://trac.osgeo.org/grass/wiki/GSoC/2018/CloudsAndShadowsDetection <
>> https://trac.osgeo.org/grass/wiki/GSoC/2018/CloudsAndShadowsDetection>
>>
>> /Images to showcase the project:/
>> i.sentinel.mask
>> https://raw.githubusercontent.com/RobiFag/GRASS_clouds_and_s
>> hadows/master/images/i_sentinel_mask_GWF.png <
>> https://raw.githubusercontent.com/RobiFag/GRASS_clouds_and_
>> shadows/master/images/i_sentinel_mask_GWF.png>
>> https://raw.githubusercontent.com/RobiFag/GRASS_clouds_and_s
>> hadows/master/images/i_sentinel_mask_CD.png <
>> https://raw.githubusercontent.com/RobiFag/GRASS_clouds_and_
>> shadows/master/images/i_sentinel_mask_CD.png>
>> https://raw.githubusercontent.com/RobiFag/GRASS_clouds_and_s
>> hadows/master/images/i_sentinel_mask_SD.png <
>> https://raw.githubusercontent.com/RobiFag/GRASS_clouds_and_
>> shadows/master/images/i_sentinel_mask_SD.png>
>> https://raw.githubusercontent.com/RobiFag/GRASS_clouds_and_s
>> hadows/master/images/i_sentinel_mask_CS.png <
>> https://raw.githubusercontent.com/RobiFag/GRASS_clouds_and_
>> shadows/master/images/i_sentinel_mask_CS.png>
>> https://raw.githubusercontent.com/RobiFag/GRASS_clouds_and_s
>> hadows/master/images/i_sentinel_mask_ES.png <
>> https://raw.githubusercontent.com/RobiFag/GRASS_clouds_and_
>> shadows/master/images/i_sentinel_mask_ES.png>
>> i.sentinel.preproc
>> https://raw.githubusercontent.com/RobiFag/GRASS_clouds_and_s
>> hadows/master/images/i_sentinel_preproc_GWF.png <
>> https://raw.githubusercontent.com/RobiFag/GRASS_clouds_and_
>> shadows/master/images/i_sentinel_preproc_GWF.png>
>>
>>
>> Kind regards,
>> Roberta
>>
>>
>
>
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