data_sources.satellite

Satellite data sources and functions

data_sources.satellite.satellite_model

Model for output of satellite data

Satellite Objects

class Satellite(DataSourceOutput)

Class to store satellite data as a xr.Dataset with some validation

model_validation

@classmethod
def model_validation(cls, v)

Check that all values are non negative

data_sources.satellite.satellite_data_source

Satellite Data Source

SatelliteDataSource Objects

@dataclass
class SatelliteDataSource(ZarrDataSource)

Satellite Data Source.

__post_init__

def __post_init__(image_size_pixels: int, meters_per_pixel: int)

Post Init

open

def open() -> None

Open Satellite data

We don't want to open_sat_data in init. If we did that, then we couldn't copy SatelliteDataSource instances into separate processes. Instead, call open() after creating separate processes.

datetime_index

def datetime_index(remove_night: bool = True) -> pd.DatetimeIndex

Returns a complete list of all available datetimes

Arguments:

  • remove_night - If True then remove datetimes at night. We're interested in forecasting solar power generation, so we don't care about nighttime data :)

In the UK in summer, the sun rises first in the north east, and sets last in the north west [1]. In summer, the north gets more hours of sunshine per day.

In the UK in winter, the sun rises first in the south east, and sets last in the south west [2]. In winter, the south gets more hours of sunshine per day.

Summer Winter
Sun rises first in N.E. S.E.
Sun sets last in N.W. S.W.
Most hours of sunlight North South

Before training, we select timesteps which have at least some sunlight. We do this by computing the clearsky global horizontal irradiance (GHI) for the four corners of the satellite imagery, and for all the timesteps in the dataset. We only use timesteps where the maximum global horizontal irradiance across all four corners is above some threshold.

The 'clearsky solar irradiance' is the amount of sunlight we'd expect on a clear day at a specific time and location. The SI unit of irradiance is watt per square meter. The 'global horizontal irradiance' (GHI) is the total sunlight that would hit a horizontal surface on the surface of the Earth. The GHI is the sum of the direct irradiance (sunlight which takes a direct path from the Sun to the Earth's surface) and the diffuse horizontal irradiance (the sunlight scattered from the atmosphere). For more info, see: https://en.wikipedia.org/wiki/Solar_irradiance

References:

  1. Video of June 2019
  2. Video of Jan 2019

open_sat_data

def open_sat_data(zarr_path: str, consolidated: bool) -> xr.DataArray

Lazily opens the Zarr store.

Adds 1 minute to the 'time' coordinates, so the timestamps are at 00, 05, ..., 55 past the hour.

Arguments:

  • zarr_path - Cloud URL or local path. If GCP URL, must start with 'gs://'
  • consolidated - Whether or not the Zarr metadata is consolidated.