night lights: added plot routine to check if data is loaded properly. also added flip check.

.gitignore

@@ -42,3 +42,7 @@ Thumbs.db
 # data folder #
 ###############
 /data/
+
+# check plot folder #
+#####################
+/plots/
\ No newline at end of file

requirements.txt

@@ -11,4 +11,4 @@ requests>=2.19.1
 pip>=10.0.1
 setuptools>=39.1.0
 wheel>=0.32.2
-
+matplotlib>=3.1.0

stable_night_lights/nightlights_file_extraction.py

@@ -10,6 +10,9 @@ import numpy as np
 import os
 from toar_location_services.settings import DATA_DIR, DEBUG, USE_DUMMY_STABLE_NIGHT_LIGHTS_DATA
 from django.contrib.gis.gdal import GDALRaster
+import matplotlib.pyplot as plt
+# import gdal
+# from gdalconst import GA_ReadOnly
 
 
 def read_proxydata(filename, dummy=DEBUG and USE_DUMMY_STABLE_NIGHT_LIGHTS_DATA):
@@ -27,21 +30,31 @@ def read_proxydata(filename, dummy=DEBUG and USE_DUMMY_STABLE_NIGHT_LIGHTS_DATA)
         print("Opening ", NIGHTLIGHTS_FILE, "...")
     rst = GDALRaster(NIGHTLIGHTS_FILE, write=False)
     lon0, lat0 = rst.origin  # top left corner
-    xmin, ymin, xmax, ymax = rst.extent  # xmin/lon0, ymin, xmax, ymax/lat0
+    xmin, ymin, xmax, ymax = rst.extent  # xmin=lon0, ymin, xmax, ymax=lat0
     cols = rst.width
     rows = rst.height
-    dlon, dlat = rst.scale  # xscale/dlon, yscale/dlat
-
-    # rst.width*xscale + xmin == xmax
+    dlon, dlat = rst.scale  # xscale=dlon, yscale=dlat
 
     # construct data array and lonvec, latvec
     data = rst.bands[0].data()
     lonvec = np.linspace(xmin, xmax, cols)
     latvec = np.linspace(ymin, ymax, rows)
 
+    # check if data is flipped
+    lat1 = lat0 + dlat * rows
+    if lat1 < lat0:
+        lat0, lat1 = lat1, lat0
+        latvec = np.flipud(latvec)
+
     # set metadata
     boundingbox = [lon0, latvec.min(), lonvec.max(), lat0]
 
+    # plot data
+    if DEBUG:
+        plt.contourf(lonvec, latvec, data)
+        plt.savefig('../plots/global_nighttime_lights.png')
+        plt.close()
+
     #
     datainfo = {'size': (rows, cols), 'resolution': (np.abs(dlon), np.abs(dlat)),
                 'boundingbox': boundingbox}

stable_night_lights/tests.py

 from django.test import TestCase
 
 # Create your tests here.
+
+from nightlights_file_extraction import read_proxydata
+
+
+FILENAME = "stable_lights_europe.tif"
+
+
+read_proxydata(FILENAME, dummy=False)