Weather Software > Station Software Development

Cloud Cover

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Bushman:
Well done!  There was someone here who did the same thing only using their local webcam image.  Can you share your Python code?

marshad:
Ok for brevity I am assuming that people know how to get a image from a url at regular intervals.

You can create a url with the satellite image centred on your location here: https://en.sat24.com/en/freeimages

Use the 300x300px option.

Here is the python code (with apologies to real python programmers)

# Important the python PIL library needs to be installed

import os, sys
import Image
import json

# This gets a value for the altitude of the Sun to decide which image to use
# You could use time instead if you haven't got access to a similar value
almanac = open('/var/www/html/VillarPerosa/jsondata/almanac.txt')
data = json.load(almanac)
sun = data["sunalt"]
almanac.close()

pixarray = []

# change the filepaths to the location of the images
if sun > 8:
    im = Image.open("/var/www/html/VillarPerosa/sat1.png")
 
else:
    im = Image.open("/var/www/html/VillarPerosa/sat2.png")
   
# this converts the image to grayscale   
im = im.convert('L')

# coordinates for the box at the centre of the image
xpos1 = 145
xpos2 = 155
ypos1 = 145
ypos2 = 155


pix = im.load()

# creates an array with the individual pixel values in the box
for y in range(ypos1,ypos2):
    for x in range(xpos1,xpos2):

        pixarray.append(pix[x,y])
      
# takes the average
pixavg = sum(pixarray) / float(len(pixarray))

# calibration, min = totally clear, max = totally overcast
min = 50
max = 250

# an adjustment to align the infrared sat with the visible       
adj =  60 * (255 - pixavg)/255
s = pixavg + adj

if sun > 8:
    s = pixavg

# cloud cover %   
s = (s - min)*100/(max - min)

# result written to a txt file for import into the weewx database.
text_file = open("cloud.txt", "w")
text_file.write(str(s))
text_file.close()   

im.close()

Good luck with it!

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

noctilucent:
What dashboard software are you using to display all that?  It looks pretty impressive.

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