reskit.util.topography

Attributes

ext

Functions

visibility_from_topography(lon, lat, elevation_raster)

Determine visibility around a given point based on topography. Also

Module Contents

reskit.util.topography.visibility_from_topography(lon, lat, elevation_raster, base_elevation=None, eye_level=2, max_degree=0.1, degree_step=0.003, theta_step=3, _interpolation='cubic')

Determine visibility around a given point based on topography. Also gives planar angle, planar elevation, and planar distance of multiple sample points surroudning the specified latitude and longitude

Params:

lon : longitude point to consider lat : latitude point to consider elevation_raster : The raster to extract elevation values from eye_level : The height to measure visibility from (in meters) above the elevation at the center point base_elevation : The total height to measure visibility from (in meters)

• If given, ‘eye_level’ is ignored

max_degree : The maximum distance to consider (in degrees) degree_step : approximate radial degree discretization theta_step : theta discretization

Return:

dict

• All items are pandas DataFrames

  • Columns match to theta direction (in radians)

• Items include:

  • latitude : the latitude at each sample point

  • longitude : the longitude at each sample point

  • planar_angle : the angle between the view point and the sample point

  • planar_dist : the planar distance between the view point and the sample point

  • planar_elev : the planar elevation of the sample point

  • visibility : indicates if the sample point should be visible from the view point

Note:

• This algorithm will likely fail if used too near to the poles

• It is also important to choose an appropriate degree_step for the given elevation raster file. If the step size is too small, artifacts will begin to appear in leading to reduced visibility - Todo: investigate this further?? (It has something to do with

  the interpolation

  • For now, choose a value which is slightly higher than the raster’s pixel resolution

• You can plot the outputs nicely with:

  >>> fig = plt.figure()
  >>> ax = (
  ...     fig.add_subplot(
  ...         111,
  ...         polar=True,
  ...     )
  ... )
  >>> h = ax.pcolormesh(a['visibility'].columns,
  >>>                   a['visibility'].index,
  >>>                   a['visibility'])
  >>> plt.colorbar(h)
  >>> plt.show()
  

reskit.util.topography.ext