xrspatial.aspect.aspect¶

xrspatial.aspect.aspect(agg: xarray.core.dataarray.DataArray, name: Optional[str] = 'aspect') → xarray.core.dataarray.DataArray[source]¶

Calculates the aspect value of an elevation aggregate.

Calculates, for all cells in the array, the downward slope direction of each cell based on the elevation of its neighbors in a 3x3 grid. The value is measured clockwise in degrees with 0 and 360 at due north. Flat areas are given a value of -1. Values along the edges are not calculated.

Parameters

agg (xarray.DataArray) – 2D NumPy, CuPy, NumPy-backed Dask, or Cupy-backed Dask array of elevation values.
name (str, default='aspect') – Name of ouput DataArray.

Returns

aspect_agg – 2D aggregate array of calculated aspect values. All other input attributes are preserved.

Return type

xarray.DataArray of the same type as agg

References

arcgis: http://desktop.arcgis.com/en/arcmap/10.3/tools/spatial-analyst-toolbox/how-aspect-works.htm#ESRI_SECTION1_4198691F8852475A9F4BC71246579FAA # noqa

Examples

import matplotlib.pyplot as plt
import numpy as np
import xarray as xr

from xrspatial import generate_terrain, aspect

# Generate Example Terrain
W = 800
H = 600

template_terrain = xr.DataArray(np.zeros((H, W)))
x_range=(-20e6, 20e6)
y_range=(-20e6, 20e6)

terrain_agg = generate_terrain(
    template_terrain, x_range=x_range, y_range=y_range, seed=1, zfactor=1000
)

# Edit Attributes
terrain_agg = terrain_agg.assign_attrs(
    {
        'Description': 'Example Terrain',
        'units': 'km',
        'Max Elevation': '4000',
    }
)

terrain_agg = terrain_agg.rename({'x': 'lon', 'y': 'lat'})
terrain_agg = terrain_agg.rename('Elevation')

# Create Aspect Aggregate Array
aspect_agg = aspect(agg = terrain_agg, name = 'Aspect')

# Edit Attributes
aspect_agg = aspect_agg.assign_attrs(
    {
        'Description': 'Example Aspect',
        'units': 'deg',
    }
)

# Plot Terrain
terrain_agg.plot(cmap = 'terrain', aspect = 2, size = 4)
plt.title("Terrain")
plt.ylabel("latitude")
plt.xlabel("longitude")

# Plot Aspect
aspect_agg.plot(aspect = 2, size = 4)
plt.title("Aspect")
plt.ylabel("latitude")
plt.xlabel("longitude")

../../_images/xrspatial-aspect-aspect-1_00.png — (png, hires.png, pdf)¶

../../_images/xrspatial-aspect-aspect-1_01.png — (png, hires.png, pdf)¶

>>> print(terrain_agg[200:203, 200:202])
<xarray.DataArray 'Elevation' (lat: 3, lon: 2)>
array([[707.57051795, 704.3194383 ],
       [706.36271613, 705.4514285 ],
       [699.46372883, 703.7514251 ]])
Coordinates:
* lon      (lon) float64 -9.975e+06 -9.925e+06
* lat      (lat) float64 -6.633e+06 -6.567e+06 -6.5e+06
Attributes:
    res:            (50000.0, 66666.66666666667)
    Description:    Example Terrain
    units:          km
    Max Elevation:  4000

>>> print(aspect_agg[200:203, 200:202])
<xarray.DataArray 'Aspect' (lat: 3, lon: 2)>
array([[155.07530658, 146.26526699],
       [194.81685088, 136.55836607],
       [203.14170549, 187.97760934]])
Coordinates:
* lon      (lon) float64 -9.975e+06 -9.925e+06
* lat      (lat) float64 -6.633e+06 -6.567e+06 -6.5e+06
Attributes:
    res:            (50000.0, 66666.66666666667)
    Description:    Example Aspect
    units:          deg
    Max Elevation:  4000

Surface

xrspatial.curvature.curvature