def apply(image):
date = image.date()
footprint = determine_footprint(image)
(sunAz, sunZen) = sun_angles.create(date, footprint)
(viewAz, viewZen) = view_angles.create(footprint)
(kvol, kvol0) = _kvol(sunAz, sunZen, viewAz, viewZen)
return _apply(image, kvol.multiply(PI()), kvol0.multiply(PI()))
def apply(image):
date = ee.Date(ee.Number(image.get('system:time_start')))
footprint = determine_footprint(image)
(sunAz, sunZen) = sun_angles.create(date, footprint)
(viewAz, viewZen) = view_angles.create(footprint)
(kvol, kvol0) = _kvol(sunAz, sunZen, viewAz, viewZen)
return _apply(image, kvol.multiply(PI), kvol0.multiply(PI))
def brdf(self, img):
def _apply(image, kvol, kvol0):
blue = _correct_band(image,
'blue',
kvol,
kvol0,
f_iso=0.0774,
f_geo=0.0079,
f_vol=0.0372)
green = _correct_band(image,
'green',
kvol,
kvol0,
f_iso=0.1306,
f_geo=0.0178,
f_vol=0.0580)
red = _correct_band(image,
'red',
kvol,
kvol0,
f_iso=0.1690,
f_geo=0.0227,
f_vol=0.0574)
re1 = _correct_band(image,
're1',
kvol,
kvol0,
f_iso=0.2085,
f_geo=0.0256,
f_vol=0.0845)
re2 = _correct_band(image,
're2',
kvol,
kvol0,
f_iso=0.2316,
f_geo=0.0273,
f_vol=0.1003)
re3 = _correct_band(image,
're3',
kvol,
kvol0,
f_iso=0.2599,
f_geo=0.0294,
f_vol=0.1197)
nir1 = _correct_band(image,
'nir1',
kvol,
kvol0,
f_iso=0.3093,
f_geo=0.0330,
f_vol=0.1535)
nir2 = _correct_band(image,
'nir2',
kvol,
kvol0,
f_iso=0.2907,
f_geo=0.0410,
f_vol=0.1611)
swir1 = _correct_band(image,
'swir1',
kvol,
kvol0,
f_iso=0.3430,
f_geo=0.0453,
f_vol=0.1154)
swir2 = _correct_band(image,
'swir2',
kvol,
kvol0,
f_iso=0.2658,
f_geo=0.0387,
f_vol=0.0639)
return replace_bands(
image,
[blue, green, red, re1, re2, re3, nir1, nir2, swir1, swir2])
def _correct_band(image, band_name, kvol, kvol0, f_iso, f_geo, f_vol):
"""fiso + fvol * kvol + fgeo * kgeo"""
iso = ee.Image(f_iso)
geo = ee.Image(f_geo)
vol = ee.Image(f_vol)
pred = vol.multiply(kvol).add(geo.multiply(kvol)).add(iso).rename(
['pred'])
pred0 = vol.multiply(kvol0).add(
geo.multiply(kvol0)).add(iso).rename(['pred0'])
cfac = pred0.divide(pred).rename(['cfac'])
corr = image.select(band_name).multiply(cfac).rename([band_name])
return corr
def _kvol(sunAz, sunZen, viewAz, viewZen):
"""Calculate kvol kernel.
From Lucht et al. 2000
Phase angle = cos(solar zenith) cos(view zenith) + sin(solar zenith) sin(view zenith) cos(relative azimuth)"""
relative_azimuth = sunAz.subtract(viewAz).rename(['relAz'])
pa1 = viewZen.cos() \
.multiply(sunZen.cos())
pa2 = viewZen.sin() \
.multiply(sunZen.sin()) \
.multiply(relative_azimuth.cos())
phase_angle1 = pa1.add(pa2)
phase_angle = phase_angle1.acos()
p1 = ee.Image(PI().divide(2)).subtract(phase_angle)
p2 = p1.multiply(phase_angle1)
p3 = p2.add(phase_angle.sin())
p4 = sunZen.cos().add(viewZen.cos())
p5 = ee.Image(PI().divide(4))
kvol = p3.divide(p4).subtract(p5).rename(['kvol'])
viewZen0 = ee.Image(0)
pa10 = viewZen0.cos() \
.multiply(sunZen.cos())
pa20 = viewZen0.sin() \
.multiply(sunZen.sin()) \
.multiply(relative_azimuth.cos())
phase_angle10 = pa10.add(pa20)
phase_angle0 = phase_angle10.acos()
p10 = ee.Image(PI().divide(2)).subtract(phase_angle0)
p20 = p10.multiply(phase_angle10)
p30 = p20.add(phase_angle0.sin())
p40 = sunZen.cos().add(viewZen0.cos())
p50 = ee.Image(PI().divide(4))
kvol0 = p30.divide(p40).subtract(p50).rename(['kvol0'])
return (kvol, kvol0)
date = img.date()
footprint = determine_footprint(img)
footprint = ee.List(
img.geometry().bounds().bounds().coordinates().get(0))
(sunAz, sunZen) = sun_angles.create(date, footprint)
(viewAz, viewZen) = view_angles.create(footprint)
(kvol, kvol0) = _kvol(sunAz, sunZen, viewAz, viewZen)
bandNames = img.bandNames()
otherBands = bandNames.removeAll(self.env.divideBands)
others = img.select(otherBands)
img = ee.Image(_apply(img, kvol.multiply(PI()), kvol0.multiply(PI())))
return img
