import pystac
from pystac import Extensions
from pystac.item import Item
from pystac.extensions.base import (ItemExtension, ExtensionDefinition, ExtendedObject)
from typing import Optional
[docs]class ViewItemExt(ItemExtension):
"""ViewItemExt is the extension of the Item in the View Geometry Extension.
View Geometry adds metadata related to angles of sensors and other radiance angles
that affect the view of resulting data. It will often be combined with other extensions that
describe the actual data, such as the eo, sat or sar extensions.
Args:
item (Item): The item to be extended.
Attributes:
item (Item): The Item that is being extended.
Note:
Using ViewItemExt to directly wrap an item will add the 'view' extension ID to
the item's stac_extensions.
"""
def __init__(self, item):
if item.stac_extensions is None:
item.stac_extensions = [Extensions.VIEW]
elif Extensions.VIEW not in item.stac_extensions:
item.stac_extensions.append(Extensions.VIEW)
self.item = item
[docs] def apply(self,
off_nadir: Optional[float] = None,
incidence_angle: Optional[float] = None,
azimuth: Optional[float] = None,
sun_azimuth: Optional[float] = None,
sun_elevation: Optional[float] = None):
"""Applies View Geometry extension properties to the extended Item.
Args:
off_nadir (float): The angle from the sensor between nadir (straight down)
and the scene center. Measured in degrees (0-90).
incidence_angle (float): The incidence angle is the angle between the vertical (normal)
to the intercepting surface and the line of sight back to the satellite at
the scene center. Measured in degrees (0-90).
azimuth (float): Viewing azimuth angle. The angle measured from the sub-satellite
point (point on the ground below the platform) between the scene center and true
north. Measured clockwise from north in degrees (0-360).
sun_azimuth (float): Sun azimuth angle. From the scene center point on the ground, this
is the angle between truth north and the sun. Measured clockwise in degrees (0-360).
sun_elevation (float): Sun elevation angle. The angle from the tangent of the scene
center point to the sun. Measured from the horizon in degrees (0-90).
"""
if (off_nadir is None and incidence_angle is None and azimuth is None
and sun_azimuth is None and sun_elevation is None):
raise pystac.STACError(
'Must provide at least one of: off_nadir, incidence_angle, azimuth, sun_azimuth, sun_elevation' # noqa: E501
)
if off_nadir:
self.off_nadir = off_nadir
if incidence_angle:
self.incidence_angle = incidence_angle
if azimuth:
self.azimuth = azimuth
if sun_azimuth:
self.sun_azimuth = sun_azimuth
if sun_elevation:
self.sun_elevation = sun_elevation
@property
def off_nadir(self):
"""Get or sets the angle from the sensor between nadir (straight down)
and the scene center. Measured in degrees (0-90).
Returns:
float
"""
return self.get_off_nadir()
@off_nadir.setter
def off_nadir(self, v):
self.set_off_nadir(v)
[docs] def get_off_nadir(self, asset=None):
"""Gets an Item or an Asset off_nadir.
If an Asset is supplied and the Item property exists on the Asset,
returns the Asset's value. Otherwise returns the Item's value
Returns:
float
"""
if asset is None or 'view:off_nadir' not in asset.properties:
return self.item.properties.get('view:off_nadir')
else:
return asset.properties.get('view:off_nadir')
[docs] def set_off_nadir(self, off_nadir, asset=None):
"""Set an Item or an Asset off_nadir.
If an Asset is supplied, sets the property on the Asset.
Otherwise sets the Item's value.
"""
self._set_property('view:off_nadir', off_nadir, asset)
@property
def incidence_angle(self):
"""Get or sets the incidence angle is the angle between the vertical (normal)
to the intercepting surface and the line of sight back to the satellite at
the scene center. Measured in degrees (0-90).
Returns:
float
"""
return self.get_incidence_angle()
@incidence_angle.setter
def incidence_angle(self, v):
self.set_incidence_angle(v)
[docs] def get_incidence_angle(self, asset=None):
"""Gets an Item or an Asset incidence_angle.
If an Asset is supplied and the Item property exists on the Asset,
returns the Asset's value. Otherwise returns the Item's value
Returns:
float
"""
if asset is None or 'view:incidence_angle' not in asset.properties:
return self.item.properties.get('view:incidence_angle')
else:
return asset.properties.get('view:incidence_angle')
[docs] def set_incidence_angle(self, incidence_angle, asset=None):
"""Set an Item or an Asset incidence_angle.
If an Asset is supplied, sets the property on the Asset.
Otherwise sets the Item's value.
"""
self._set_property('view:incidence_angle', incidence_angle, asset)
@property
def azimuth(self):
"""Get or sets the viewing azimuth angle. The angle measured from the sub-satellite
point (point on the ground below the platform) between the scene center and true
north. Measured clockwise from north in degrees (0-360).
Returns:
float
"""
return self.get_azimuth()
@azimuth.setter
def azimuth(self, v):
self.set_azimuth(v)
[docs] def get_azimuth(self, asset=None):
"""Gets an Item or an Asset azimuth.
If an Asset is supplied and the Item property exists on the Asset,
returns the Asset's value. Otherwise returns the Item's value
Returns:
float
"""
if asset is None or 'view:azimuth' not in asset.properties:
return self.item.properties.get('view:azimuth')
else:
return asset.properties.get('view:azimuth')
[docs] def set_azimuth(self, azimuth, asset=None):
"""Set an Item or an Asset azimuth.
If an Asset is supplied, sets the property on the Asset.
Otherwise sets the Item's value.
"""
self._set_property('view:azimuth', azimuth, asset)
@property
def sun_azimuth(self):
"""Get or sets the sun azimuth angle. From the scene center point on the ground, this
is the angle between truth north and the sun. Measured clockwise in degrees (0-360).
Returns:
float
"""
return self.get_sun_azimuth()
@sun_azimuth.setter
def sun_azimuth(self, v):
self.set_sun_azimuth(v)
[docs] def get_sun_azimuth(self, asset=None):
"""Gets an Item or an Asset sun_azimuth.
If an Asset is supplied and the Item property exists on the Asset,
returns the Asset's value. Otherwise returns the Item's value
Returns:
float
"""
if asset is None or 'view:sun_azimuth' not in asset.properties:
return self.item.properties.get('view:sun_azimuth')
else:
return asset.properties.get('view:sun_azimuth')
[docs] def set_sun_azimuth(self, sun_azimuth, asset=None):
"""Set an Item or an Asset sun_azimuth.
If an Asset is supplied, sets the property on the Asset.
Otherwise sets the Item's value.
"""
self._set_property('view:sun_azimuth', sun_azimuth, asset)
@property
def sun_elevation(self):
"""Get or sets the sun elevation angle. The angle from the tangent of the scene
center point to the sun. Measured from the horizon in degrees (0-90).
Returns:
float
"""
return self.get_sun_elevation()
@sun_elevation.setter
def sun_elevation(self, v):
self.set_sun_elevation(v)
[docs] def get_sun_elevation(self, asset=None):
"""Gets an Item or an Asset sun_elevation.
If an Asset is supplied and the Item property exists on the Asset,
returns the Asset's value. Otherwise returns the Item's value
Returns:
float
"""
if asset is None or 'view:sun_elevation' not in asset.properties:
return self.item.properties.get('view:sun_elevation')
else:
return asset.properties.get('view:sun_elevation')
[docs] def set_sun_elevation(self, sun_elevation, asset=None):
"""Set an Item or an Asset sun_elevation.
If an Asset is supplied, sets the property on the Asset.
Otherwise sets the Item's value.
"""
self._set_property('view:sun_elevation', sun_elevation, asset)
@classmethod
def _object_links(cls):
return []
[docs] @classmethod
def from_item(cls, item):
return cls(item)
VIEW_EXTENSION_DEFINITION = ExtensionDefinition(Extensions.VIEW,
[ExtendedObject(Item, ViewItemExt)])
