l3py.gravityfield¶
Representations of Earth’s gravity field.
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gravityfield.
degree_indices
()¶ Return array indices for all coeffcients of degree n.
The coefficients are ordered by trigonometric function (first all cosine coefficients then all sine coefficients) with increasing order.
Parameters: n (int) – degree Returns: - rows (array_like(k,)) – row indices of all coefficients of degree n
- columns (array_like(k,)) – column indices of all coefficients of degree n
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gravityfield.
order_indices
(m)¶ Return array indices for all coeffcients of order m.
The coefficients are ordered by trigonometric function (first all cosine coefficients then all sine coefficients) with increasing degree.
Parameters: - maximum_degree (int) – maximum degree of target coefficient array
- m (int) – order
Returns: - rows (array_like(k,)) – row indices of all coefficients of order m
- columns (array_like(k,)) – column indices of all coefficients of order m
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class
l3py.gravityfield.
PotentialCoefficients
(GM=398600441500000.0, R=6378136.3)[source]¶ Class representation of a set of (possibly time stamped) potential coefficients.
Parameters: - GM (float) – geocentric gravitational constant
- R (float) – reference radius
Methods
append
(trigonometric_function, degree, …)Append a coefficient to a PotentialCoefficients instance. coefficient_triangle
([min_degree, max_degree])Arrange spherical harmonic coefficients as triangle for visualization. copy
()Return a deep copy of the PotentialCoefficients instance. degree_amplitudes
([kernel])Compute degree amplitudes from potential coefficients. nmax
()Return maximum spherical harmonic degree of a PotentialCoefficients instance. replace_c20
(gravityfield)Replace the c20 coefficient of a PotentialCoefficients instance by c20 of another PotentialCoefficients instance. slice
([min_degree, max_degree, min_order, …])Slice a PotentialCoefficients instance to a specific degree and order range. to_grid
([grid, kernel])Compute gridded values from a set of potential coefficients. truncate
(nmax)Truncate a PotentialCoefficients instance to a new maximum spherical harmonic degree. -
append
(trigonometric_function, degree, order, value)[source]¶ Append a coefficient to a PotentialCoefficients instance.
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coefficient_triangle
(min_degree=2, max_degree=None)[source]¶ Arrange spherical harmonic coefficients as triangle for visualization.
Parameters: - min_degree (int) – degrees below min_degree are masked out
- max_degree (int) – triangle is truncated at max_degree
Returns: triangle
Return type: masked_array shape (max_degree+1, 2*max_degree-1)
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degree_amplitudes
(kernel='potential')[source]¶ Compute degree amplitudes from potential coefficients.
Parameters: kernel (string) – name of kernel for the degree amplitude computation Returns: - degrees (array_like shape (self.nmax()+1,)) – integer sequence of degrees
- amplitudes (array_like shape (self.nmax()+1,)) – computed degree amplitudes
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replace_c20
(gravityfield)[source]¶ Replace the c20 coefficient of a PotentialCoefficients instance by c20 of another PotentialCoefficients instance. Substitution is performed in-place.
Parameters: gravityfield (PotentialCoefficients instance) – gravity field containing the new c20 value
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slice
(min_degree=None, max_degree=None, min_order=None, max_order=None, step_degree=1, step_order=1)[source]¶ Slice a PotentialCoefficients instance to a specific degree and order range. Return value is a new PotentialCoefficients instance, the original gravity field is unchanged.
Parameters: - min_degree (int) – minimum degree of sliced PotentialCoefficients (Default: 0)
- max_degree (int) – maximum degree of sliced PotentialCoefficients (Default: maximum degree if calling object)
- min_order (int) – minimum order of sliced PotentialCoefficients (Default: 0)
- max_order (int) – maximum order of sliced PotentialCoefficients (Default: max_degree)
- step_degree (int) – step between min_degree and max_degree (Default: 1)
- step_order (int) – step between min_order and max_order (Default: 1)
Returns: gravityfield – new PotentialCoefficients instance with all coefficients outside of the passed degree and order ranges set to zero
Return type:
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to_grid
(grid=<l3py.grid.GeographicGrid object>, kernel='ewh')[source]¶ Compute gridded values from a set of potential coefficients.
Parameters: - gravityfield (PotentialCoefficients instance) – potential coefficients to be gridded
- grid (instance of Grid subclass) – point distribution (Default: 0.5x0.5 degree geographic grid)
- kernel (string) – gravity field functional to be gridded (Default: equivalent water height). See Kernel for details.
Returns: output_grid – deep copy of the input grid with the gridded values
Return type: instance of type(grid)