def calc_aspect_at_node(
grid,
slope_component_tuple=None,
elevs="topographic__elevation",
unit="degrees",
ignore_closed_nodes=True,
):
"""Get array of aspect of a surface.
Calculates at returns the aspect of a surface. Aspect is returned as
radians clockwise of north, unless input parameter units is set to
'degrees'.
If slope_component_tuple is provided, i.e., (slope_x, slope_y), the
aspect will be calculated from these data.
If it is not, it will be derived from elevation data at the nodes,
which can either be a string referring to a grid field (default:
'topographic__elevation'), or an nnodes-long numpy array of the
values themselves.
If ignore_closed_nodes is False, all proximal elevation values will be used
in the calculation. If True, only unclosed nodes are used.
Parameters
----------
grid : ModelGrid
A ModelGrid.
slope_component_tuple : (slope_x_array, slope_y_array) (optional)
Tuple of components of slope in the x and y directions, defined
on nodes, if already known. If not, provide *elevs*.
elevs : str or array (optional)
Node field name or node array of elevations.
If *slope_component_tuple* is not provided, must be set, but unused
otherwise.
unit : {'degrees', 'radians'}
Controls the unit that the aspect is returned as.
ignore_closed_nodes : bool
If True, do not incorporate values at closed nodes into the calc.
Examples
--------
>>> from landlab import RasterModelGrid
>>> mg = RasterModelGrid((4, 4))
>>> z = mg.node_x ** 2 + mg.node_y ** 2
>>> mg.calc_aspect_at_node(elevs=z)
array([ 225. , 240.16585039, 255.2796318 , 258.69006753,
209.83414961, 225. , 243.54632481, 248.77808974,
194.7203682 , 206.45367519, 225. , 231.94498651,
191.30993247, 201.22191026, 218.05501349, 225. ])
>>> z = z.max() - z
>>> mg.calc_aspect_at_node(elevs=z)
array([ 45. , 60.16585039, 75.2796318 , 78.69006753,
29.83414961, 45. , 63.54632481, 68.77808974,
14.7203682 , 26.45367519, 45. , 51.94498651,
11.30993247, 21.22191026, 38.05501349, 45. ])
>>> mg = RasterModelGrid((4, 4), xy_spacing=(3., 2.))
>>> z = mg.node_x ** 2 + mg.node_y ** 2
>>> mg.calc_aspect_at_node(elevs=z)
array([ 236.30993247, 247.52001262, 259.97326008, 262.40535663,
220.75264634, 234.41577266, 251.13402374, 255.29210302,
201.54258265, 215.47930877, 235.73541937, 242.24162456,
196.69924423, 209.43534223, 229.19345757, 236.30993247])
Note that a small amount of asymmetry arises at the grid edges due
to the "missing" nodes beyond the edge of the grid.
LLCATS: NINF SURF
"""
if slope_component_tuple:
if not isinstance(slope_component_tuple, (tuple, list)):
raise TypeError("slope_component_tuple must be tuple")
if len(slope_component_tuple) != 2:
raise ValueError("slope_component_tuple must be of length 2")
else:
try:
elev_array = grid.at_node[elevs]
except (KeyError, TypeError):
assert elevs.size == grid.number_of_nodes
elev_array = elevs
_, slope_component_tuple = grid.calc_slope_at_node(
elevs=elev_array,
ignore_closed_nodes=ignore_closed_nodes,
return_components=True,
)
angle_from_x_ccw = np.arctan2(-slope_component_tuple[1], -slope_component_tuple[0])
if unit == "degrees":
return radians_to_degrees(angle_from_x_ccw)
elif unit == "radians":
angle_from_north_cw = (5. * np.pi / 2. - angle_from_x_ccw) % (2. * np.pi)
return angle_from_north_cw
else:
raise TypeError("unit must be 'degrees' or 'radians'")
def calc_aspect_at_node(
grid,
slope_component_tuple=None,
elevs="topographic__elevation",
unit="degrees",
ignore_closed_nodes=True,
):
"""Get array of aspect of a surface.
Calculates at returns the aspect of a surface. Aspect is returned as
radians clockwise of north, unless input parameter units is set to
'degrees'.
If slope_component_tuple is provided, i.e., (slope_x, slope_y), the
aspect will be calculated from these data.
If it is not, it will be derived from elevation data at the nodes,
which can either be a string referring to a grid field (default:
'topographic__elevation'), or an nnodes-long numpy array of the
values themselves.
If ignore_closed_nodes is False, all proximal elevation values will be used
in the calculation. If True, only unclosed nodes are used.
Parameters
----------
grid : ModelGrid
A ModelGrid.
slope_component_tuple : (slope_x_array, slope_y_array) (optional)
Tuple of components of slope in the x and y directions, defined
on nodes, if already known. If not, provide *elevs*.
elevs : str or array (optional)
Node field name or node array of elevations.
If *slope_component_tuple* is not provided, must be set, but unused
otherwise.
unit : {'degrees', 'radians'}
Controls the unit that the aspect is returned as.
ignore_closed_nodes : bool
If True, do not incorporate values at closed nodes into the calc.
Examples
--------
>>> from landlab import RasterModelGrid
>>> mg = RasterModelGrid((4, 4))
>>> z = mg.node_x ** 2 + mg.node_y ** 2
>>> mg.calc_aspect_at_node(elevs=z)
array([ 225. , 240.16585039, 255.2796318 , 258.69006753,
209.83414961, 225. , 243.54632481, 248.77808974,
194.7203682 , 206.45367519, 225. , 231.94498651,
191.30993247, 201.22191026, 218.05501349, 225. ])
>>> z = z.max() - z
>>> mg.calc_aspect_at_node(elevs=z)
array([ 45. , 60.16585039, 75.2796318 , 78.69006753,
29.83414961, 45. , 63.54632481, 68.77808974,
14.7203682 , 26.45367519, 45. , 51.94498651,
11.30993247, 21.22191026, 38.05501349, 45. ])
>>> mg = RasterModelGrid((4, 4), xy_spacing=(3., 2.))
>>> z = mg.node_x ** 2 + mg.node_y ** 2
>>> mg.calc_aspect_at_node(elevs=z)
array([ 236.30993247, 247.52001262, 259.97326008, 262.40535663,
220.75264634, 234.41577266, 251.13402374, 255.29210302,
201.54258265, 215.47930877, 235.73541937, 242.24162456,
196.69924423, 209.43534223, 229.19345757, 236.30993247])
Note that a small amount of asymmetry arises at the grid edges due
to the "missing" nodes beyond the edge of the grid.
LLCATS: NINF SURF
"""
if slope_component_tuple:
if not isinstance(slope_component_tuple, (tuple, list)):
raise TypeError("slope_component_tuple must be tuple")
if len(slope_component_tuple) != 2:
raise ValueError("slope_component_tuple must be of length 2")
else:
try:
elev_array = grid.at_node[elevs]
except (KeyError, TypeError):
assert elevs.size == grid.number_of_nodes
elev_array = elevs
_, slope_component_tuple = grid.calc_slope_at_node(
elevs=elev_array,
ignore_closed_nodes=ignore_closed_nodes,
return_components=True,
)
angle_from_x_ccw = np.arctan2(-slope_component_tuple[1],
-slope_component_tuple[0])
if unit == "degrees":
return radians_to_degrees(angle_from_x_ccw)
elif unit == "radians":
angle_from_north_cw = (5.0 * np.pi / 2.0 - angle_from_x_ccw) % (2.0 *
np.pi)
return angle_from_north_cw
else:
raise TypeError("unit must be 'degrees' or 'radians'")