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Cloud Cover

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marshad:
Measuring cloud cover seems to be an area neglected by most amateur weather enthusiasts (or am I wrong?)
 
The problem is how to measure it. If you are lucky enough to have a METAR close by (which I haven't), you could use this as a proxy. Or use an api such as darksky to get the current conditions, but my experience is that this can be highly inaccurate. Or you could look up every half hour and record the oktas manually - but life is too short.

Instead what if you could take the latest satellite image of your location and analyse the pixels directly over your station? I have written a program in Python to do just this (I am a totally amateur programmer btw). It takes an image every 15 mins from Sat24.com, converts it to grayscale and then looks at the values of the pixels in a 10x10 pixel box above my location and returns an average. The range is 0 for black to 255 white. It is then a case of calibrating it by looking at the values of a totally clear sky and a totally overcast sky.

I have had it running for about a month now and it is remarkably accurate with the visible satellite images, slightly less so for the infrared. I am storing the data in weewx - sample chart attached.

If anybody thinks this has any merit I would be happy to share the program and would welcome any improvements from more experienced programmers.
 [ You are not allowed to view attachments ]
http://moonappreciationsociety.com/Meteo/VillarPerosa/

PaulMy:
Very nice Marshad!

It would also be interesting to compare that to a sunrecorder like the Blake-Larsen.  Unfortunately I have not yet been able to reconnect mine after our move to a new home.

Enjoy,
Paul

the beteljuice:

--- Quote ---Instead what if you could take the latest satellite image of your location and analyse the pixels directly over your station
--- End quote ---
This has great potential for eg. 'latest obs' or various forecasting scripts or .....

Keep us informed  [tup]

marshad:
Thanks Paul and beteljuice.

The script was surprisingly simple to put together and yes I agree it could be used for other things - thinking also about radar images.

David

http://moonappreciationsociety.com/Meteo/VillarPerosa/

marshad:

--- Quote from: the beteljuice on July 18, 2019, 05:43:23 PM ---
--- Quote ---Instead what if you could take the latest satellite image of your location and analyse the pixels directly over your station
--- End quote ---
This has great potential for eg. 'latest obs' or various forecasting scripts or .....

Keep us informed  [tup]

--- End quote ---

Perhaps I didn't make it clear enough that this is working now and happy to share it with anyone wanting to try it.

http://moonappreciationsociety.com/Meteo/VillarPerosa/

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