SixS#

class geowombat.radiometry.SixS[source]#

Bases: Altitude, SixSMixin

A class to handle loading, downloading and interpolating of LUTs (look up tables) used by the 6S emulator.

Parameters:

  • sensor (str) – The sensor to adjust.

  • rad_scale (Optional[float]) – The radiance scale factor. Scaled values should be in the range [0,1000].

  • angle_factor (Optional[float]) – The angle scale factor.

Example

>>> sixs = SixS('l5', verbose=1)
>>>
>>> with gw.config.update(sensor='l7'):
>>>     with gw.open('image.tif') as src, gw.open('solar_za') as sza:
>>>         sixs.rad_to_sr(src, 'blue', sza, doy, h2o=1.0, o3=0.4, aot=0.3)

Methods

rad_to_sr(data, sensor, wavelength, sza, doy)

Converts radiance to surface reflectance using a 6S radiative transfer model lookup table.

toar_to_sr(data, sensor, wavelength, sza, doy)

Converts top of atmosphere reflectance to surface reflectance using 6S outputs.

get_mean_altitude

prepare_coeff

Methods Documentation

rad_to_sr(data, sensor, wavelength, sza, doy, src_nodata=-32768, dst_nodata=-32768, angle_factor=0.01, interp_method='fast', h2o=1.0, o3=0.4, aot=0.3, altitude=0.0, n_jobs=1)[source]#

Converts radiance to surface reflectance using a 6S radiative transfer model lookup table.

Parameters:

  • data (DataArray) – The data to correct, in radiance.

  • sensor (str) – The sensor name.

  • wavelength (str) – The band wavelength to process.

  • sza (float | DataArray) – The solar zenith angle.

  • doy (int) – The day of year.

  • src_nodata (Optional[int or float]) – The input ‘no data’ value.

  • dst_nodata (Optional[int or float]) – The output ‘no data’ value.

  • angle_factor (Optional[float]) – The scale factor for angles.

  • interp_method (Optional[str]) – The LUT interpolation method. Choices are [‘fast’, ‘slow’]. ‘fast’: Uses nearest neighbor lookup with scipy.interpolate.NearestNDInterpolator. ‘slow’: Uses linear interpolation with scipy.interpolate.LinearNDInterpolator.

  • h2o (Optional[float]) – The water vapor (g/m^2). [0,8.5].

  • o3 (Optional[float]) – The ozone (cm-atm). [0,8].

  • aot (Optional[float | DataArray]) – The aerosol optical thickness (unitless). [0,3].

  • altitude (Optional[float]) – The altitude over the sensor acquisition location.

  • n_jobs (Optional[int]) – The number of parallel jobs for dask.compute.

Returns:

Data range: 0-1

Return type:

xarray.DataArray

toar_to_sr(data, sensor, wavelength, sza, doy, src_nodata=-32768, dst_nodata=-32768, angle_factor=0.01, interp_method='fast', h2o=1.0, o3=0.4, aot=0.3, altitude=0.0, n_jobs=1)[source]#

Converts top of atmosphere reflectance to surface reflectance using 6S outputs.

Parameters:

  • data (DataArray) – The top of atmosphere reflectance.

  • sensor (str) – The sensor name.

  • wavelength (str) – The band wavelength to process.

  • sza (float | DataArray) – The solar zenith angle.

  • doy (int) – The day of year.

  • src_nodata (Optional[int or float]) – The input ‘no data’ value.

  • dst_nodata (Optional[int or float]) – The output ‘no data’ value.

  • angle_factor (Optional[float]) – The scale factor for angles.

  • interp_method (Optional[str]) – The LUT interpolation method. Choices are [‘fast’, ‘slow’]. ‘fast’: Uses nearest neighbor lookup with scipy.interpolate.NearestNDInterpolator. ‘slow’: Uses linear interpolation with scipy.interpolate.LinearNDInterpolator.

  • h2o (Optional[float]) – The water vapor (g/m^2). [0,8.5].

  • o3 (Optional[float]) – The ozone (cm-atm). [0,8].

  • aot (Optional[float | DataArray]) – The aerosol optical thickness (unitless). [0,3].

  • altitude (Optional[float]) – The altitude over the sensor acquisition location.

  • n_jobs (Optional[int]) – The number of parallel jobs for dask.compute.

6S model outputs:
t_g (float): The total gaseous transmission of the atmosphere.

s.run() –> s.outputs.total_gaseous_transmittance

p_alpha (float): The atmospheric reflectance.

s.run() –> s.outputs.atmospheric_intrinsic_reflectance

s (float): The spherical albedo of the atmosphere.

s.run() –> s.outputs.spherical_albedo

t_s (float): The atmospheric transmittance from sun to target.

s.run() –> s.outputs.transmittance_total_scattering.downward

t_v (float): The atmospheric transmittance from target to satellite.

s.run() –> s.outputs.transmittance_total_scattering.upward

rad_to_sr(data, sensor, wavelength, sza, doy, src_nodata=-32768, dst_nodata=-32768, angle_factor=0.01, interp_method='fast', h2o=1.0, o3=0.4, aot=0.3, altitude=0.0, n_jobs=1)[source]#

Converts radiance to surface reflectance using a 6S radiative transfer model lookup table.

Parameters:

  • data (DataArray) – The data to correct, in radiance.

  • sensor (str) – The sensor name.

  • wavelength (str) – The band wavelength to process.

  • sza (float | DataArray) – The solar zenith angle.

  • doy (int) – The day of year.

  • src_nodata (Optional[int or float]) – The input ‘no data’ value.

  • dst_nodata (Optional[int or float]) – The output ‘no data’ value.

  • angle_factor (Optional[float]) – The scale factor for angles.

  • interp_method (Optional[str]) – The LUT interpolation method. Choices are [‘fast’, ‘slow’]. ‘fast’: Uses nearest neighbor lookup with scipy.interpolate.NearestNDInterpolator. ‘slow’: Uses linear interpolation with scipy.interpolate.LinearNDInterpolator.

  • h2o (Optional[float]) – The water vapor (g/m^2). [0,8.5].

  • o3 (Optional[float]) – The ozone (cm-atm). [0,8].

  • aot (Optional[float | DataArray]) – The aerosol optical thickness (unitless). [0,3].

  • altitude (Optional[float]) – The altitude over the sensor acquisition location.

  • n_jobs (Optional[int]) – The number of parallel jobs for dask.compute.

Returns:

Data range: 0-1

Return type:

xarray.DataArray

toar_to_sr(data, sensor, wavelength, sza, doy, src_nodata=-32768, dst_nodata=-32768, angle_factor=0.01, interp_method='fast', h2o=1.0, o3=0.4, aot=0.3, altitude=0.0, n_jobs=1)[source]#

Converts top of atmosphere reflectance to surface reflectance using 6S outputs.

Parameters:

  • data (DataArray) – The top of atmosphere reflectance.

  • sensor (str) – The sensor name.

  • wavelength (str) – The band wavelength to process.

  • sza (float | DataArray) – The solar zenith angle.

  • doy (int) – The day of year.

  • src_nodata (Optional[int or float]) – The input ‘no data’ value.

  • dst_nodata (Optional[int or float]) – The output ‘no data’ value.

  • angle_factor (Optional[float]) – The scale factor for angles.

  • interp_method (Optional[str]) – The LUT interpolation method. Choices are [‘fast’, ‘slow’]. ‘fast’: Uses nearest neighbor lookup with scipy.interpolate.NearestNDInterpolator. ‘slow’: Uses linear interpolation with scipy.interpolate.LinearNDInterpolator.

  • h2o (Optional[float]) – The water vapor (g/m^2). [0,8.5].

  • o3 (Optional[float]) – The ozone (cm-atm). [0,8].

  • aot (Optional[float | DataArray]) – The aerosol optical thickness (unitless). [0,3].

  • altitude (Optional[float]) – The altitude over the sensor acquisition location.

  • n_jobs (Optional[int]) – The number of parallel jobs for dask.compute.

6S model outputs:
t_g (float): The total gaseous transmission of the atmosphere.

s.run() –> s.outputs.total_gaseous_transmittance

p_alpha (float): The atmospheric reflectance.

s.run() –> s.outputs.atmospheric_intrinsic_reflectance

s (float): The spherical albedo of the atmosphere.

s.run() –> s.outputs.spherical_albedo

t_s (float): The atmospheric transmittance from sun to target.

s.run() –> s.outputs.transmittance_total_scattering.downward

t_v (float): The atmospheric transmittance from target to satellite.

s.run() –> s.outputs.transmittance_total_scattering.upward