[GRASS-dev] New GRASS addon i.sentinel.mask is now available (GSoC 2018 project)

[Roberta Fagandini]

Hi Ivan!

2018-06-18 12:05 GMT+02:00 Ivan Barka <ivan.barka at gmail.com>:

> Hi Roberta,
>
> thank you for your effort. I tried i.sentinel.mask just now with one
> Sentinel-2 granule. I have considerably better results with Level 2A
> Sentinel product, topographically and atmospherically corrected from Level
> 1C by sen2cor with default settings.
>

Thank you so much for testing i.sentinel.mask! If it is possible I would be
very interested in seeing your results.


>
> Regarding strange results of i.topo.corr, I also had a problem few months
> ago. In the first pass, if the resolution of DEM raster differs from
> current region settings, you can create strange illumination model. The
> solution was to set region from the DEM (e.g. with 25 m resolution in case
> of EU-DEM), then to create illumination model with "i.topo.corr -i ..."),
> restore region settings (e.g. with 30 m for Landsat) and finally to apply
> topo correction in the second pass.
> For some unknown reason, i.topo.corr did not change region settings
> automatically, despite you can find "The illumination model (cos_i) with
> flag -i uses the actual region as limits and the resolution of the
> elevation map." in its manual (Notes section).
>

Interesting! I will test i.topo.corr as you suggest.

Thank you!
Roberta


>
> Best regards,
>
> Ivan
>
>
> 2018-06-14 13:08 GMT+02:00 Stefan Blumentrath <Stefan.Blumentrath at nina.no>
> :
>
>> i.topo.corr performed quite well for us in the Norwegian mountains with
>> minnaert method…
>>
>> What options did you try in i.topo.corr?
>>
>>
>>
>> Cheers
>>
>> Stefan
>>
>>
>>
>> *From:* Roberta Fagandini <robifagandini at gmail.com>
>> *Sent:* torsdag 14. juni 2018 13:01
>> *To:* Stefan Blumentrath <Stefan.Blumentrath at nina.no>
>> *Cc:* Moritz Lennert <mlennert at club.worldonline.be>; GRASS developers
>> list <grass-dev at lists.osgeo.org>
>>
>> *Subject:* Re: [GRASS-dev] New GRASS addon i.sentinel.mask is now
>> available (GSoC 2018 project)
>>
>>
>>
>> Hi Stefan!
>>
>> Certainly applying the topographic correction could be very useful to
>> avoid misclassification.
>>
>> I did several tests with i.topo.corr but I always got strange results
>> especially in areas with steeper terrain.
>>
>> I also tested the topographic correction tool implemented in arcsi [0]
>> but again the results were not satisfactory at all. This is why I have not
>> further investigated this issue within my PhD research.
>>
>>
>>
>> In order to remove misclassifications, e.g. due to topographic shadows, I
>> implemented the shadow mask cleaning procedure. It intersects the rough
>> shadow mask with the cloud mask that is shifted according to the sun
>> position. In this way, all the areas identified as shadows without a
>> corresponding cloud are removed from the final shadow mask.
>>
>>
>>
>> I'm still very interested in investigating the topographic correction so
>> if you have any suggestion please, let me know!!
>>
>>
>>
>> Ciao,
>>
>> Roberta
>>
>>
>>
>> [0] https://www.arcsi.remotesensing.info/index.html
>>
>>
>>
>> 2018-06-14 10:55 GMT+02:00 Stefan Blumentrath <Stefan.Blumentrath at nina.no
>> >:
>>
>> Hi Roberta,
>>
>>
>>
>> What about topographic correction (i.topo.corr [1])?
>>
>> Should that be run before as well?
>>
>> I would assume it has some impact on shadow detection in steeper terrain…
>>
>>
>>
>> Cheers
>>
>> Stefan
>>
>>
>>
>> 1: https://grass.osgeo.org/grass74/manuals/i.topo.corr.html
>>
>>
>>
>> *From:* grass-dev <grass-dev-bounces at lists.osgeo.org> *On Behalf Of *Roberta
>> Fagandini
>> *Sent:* torsdag 14. juni 2018 10:29
>> *To:* Moritz Lennert <mlennert at club.worldonline.be>
>> *Cc:* GRASS developers list <grass-dev at lists.osgeo.org>
>> *Subject:* Re: [GRASS-dev] New GRASS addon i.sentinel.mask is now
>> available (GSoC 2018 project)
>>
>>
>>
>> Hi Moritz!
>>
>>
>>
>> 2018-06-14 10:03 GMT+02:00 Moritz Lennert <mlennert at club.worldonline.be>:
>>
>> On 13/06/18 17:35, Roberta Fagandini wrote:
>>
>> Hi all!
>> The first version of i.sentinel.mask is now available and can be
>> installed from the official svn repository.
>> i.sentinel.mask is a module for cloud and shadow masks computation and it
>> is the first step of my GSoC project.
>>
>>
>> Thank you, Roberta. Great job !
>>
>>
>>
>> Thank you!
>>
>>
>>
>>
>> One question: ISTR that you mentioned that the input to this module has
>> to be atmospherically corrected images, i.e. land surface reflectance. Is
>> this true ? If yes, then this needs to be mentioned in the man page.
>>
>>
>>
>> Yes, it's true! I'm going to add it.
>>
>>
>>
>> Roberta
>>
>>
>>
>>
>>
>> Moritz
>>
>>
>>
>>
>>
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>>
>
>
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