[GRASS-dev] ​GSoC 2018 report week 03 - GRASS GIS module for Sentinel-2 cloud and shadow detection

Nikos Alexandris nik at nikosalexandris.net
Mon Jun 4 02:54:01 PDT 2018

Ciao Roberta,

great work!

Moritz got me faster, as I intended to chime in, with similar

So +1 for:

- a "real" module, as Moritz described it

- for using the metadata file, and parsing it -- my experience with
  Landsat and other high-resolution satellite products, showed it's best to
  trust the individual metadata that accompany an acquisition.
  Parameters may be very specific to one single acquisition.
  Also, a module that is designed to be "dynamic" is more
  future-proof and easy to maintain and update.
  For example, reading band names from the meta-data, as opposed to more
  "static" designs, i.e. expecting specific hardcoded options, such as
  band names, or their order.

- PEP8 rules and keeping module options in separate lines to increase legibility

In line with the suggestions on style, I would stress out to fully
spell out the names of functions, options, descriptions of flags,
iterables and iterators.  It will make it easier for the next reader of
your code.

Finally, it's a good idea to write even mini-tests, while you are
progressing, for the small functions that eventually develop to keep the
full scrip compact, functional and more legible.

Writing a test, for your module, in the end, will be much easier.

I am sure you know all this. Yet, discussing it is a good thing in
my view.

Keep up the good work, Nikos

* Moritz Lennert <mlennert at club.worldonline.be> [2018-06-04 11:03:41 +0200]:

>Hi Roberta !
>On 03/06/18 14:38, Roberta Fagandini wrote:
>>Hi all!
>>I'm Roberta Fagandini and I'm working on my GSoC project, a GRASS 
>>GIS module for Sentinel-2 cloud and shadow detection.
>>This is my report for the third week of coding.
>>*1) What did I complete this week?*
>>  * Implemented some changes from dev feedback (e.g. r.univar instead of
>>    r.stats.zonal)
>>  * Tested the modified python script and fixed bugs
>>  * Prepared the python script in order to start implementing the GUI
>>  * Started implementing the GUI
>>  * Made some changes to the code depending on the GUI requirements (add
>>    controls and check on input, output and temporary file, etc.)
>>  * Cleaned up the whole code
>>  * Tested the GUI and fixed bugs
>>  * Frequently added the basic version of the GUI to my
>>    GitHub repository [0]
>>  * Shared progress with the community
>I'm sorry, I haven't had the time to test your module, yet. A few 
>recommendation, though, based on a quick read of the code. I assume 
>that the relevant file is i.sentinel.mask.
>- I would recommend to immediately create a real complete module that 
>can be installed with g.extension. This means creating a directory 
>with the module as .py file, a .html manual page file, but which could 
>be empty at the beginning, and a Makefile (see existing scripts in the 
>core code or in addons for examples). Being able to install everything 
>directly from github with a simple g.extension call makes testing much 
>- I see that all the input bands are marked as required. Are they all 
>necessary to the calculations ? If yes, aren't all these bands always 
>from the same acquisition ? If yes, then maybe we can avoid parameter 
>inflation by either just asking for a prefix and then getting all 
>bands from that prefix (following standard sentinel naming), or 
>provide the MTD file and read the band names from there, or you could 
>ask for a group name and it would be up to the user to create the 
>group before launching the module.
>- A small idea in terms of coding style: I personally think that code 
>should be as easily understandable as possible. For example: in the 
>formulas you use the f_bands[] list. Maybe you could make this into a 
>dictionary and so instead of reading f_bands[0], we would read 
>f_bands['blue'] making the formulas easier to follow.
>- Please follow PEP8 style guide (see [1]). Amongst others, this means 
>limiting lines to 79 characters. So:
>	- The general style used for gscript.*_command calls in Python scripts is
>	gscript.run_command('v.dissolve',
>			    input=tmp["centroid"],
>			    column='value',
>			    output=tmp["dissolve"],
>			    overwrite=True,
>			    quiet=True)
>	i.e. each parameter on its own line. This make it easier to read
>	and lines shorter.
>	- The same for r.mapcalc calls: if necessary you can construct
>	the individual rules over more than one line.
>I'll try to find some time this week to test the module and maybe come 
>back with some more feedback on the coding.
>Great job so far, though !
>[1] https://trac.osgeo.org/grass/wiki/Submitting/Python#Style
>grass-dev mailing list
>grass-dev at lists.osgeo.org

Nikos Alexandris | Remote Sensing & Geomatics
GPG Key Fingerprint 6F9D4506F3CA28380974D31A9053534B693C4FB3 
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