xdem.coreg.TerrainBias

class xdem.coreg.TerrainBias(terrain_attribute='maximum_curvature', fit_or_bin='bin', fit_func='norder_polynomial', fit_optimizer=<function curve_fit>, bin_sizes=100, bin_statistic=<function nanmedian>, bin_apply_method='linear', subsample=1.0)

Correct a bias according to terrain, such as elevation or curvature.

With elevation: often useful for nadir image DEM correction, where the focal length is slightly miscalculated. With curvature: often useful for a difference of DEMs with different effective resolution.

The binning and/or fitting correction parameters are stored in the self.meta[“outputs”][“fitorbin”].

DISCLAIMER: An elevation correction may introduce error when correcting non-photogrammetric biases, as generally elevation biases are interlinked with curvature biases. See Gardelle et al. (2012) (Figure 2), http://dx.doi.org/10.3189/2012jog11j175, for curvature-related biases.

__init__(terrain_attribute='maximum_curvature', fit_or_bin='bin', fit_func='norder_polynomial', fit_optimizer=<function curve_fit>, bin_sizes=100, bin_statistic=<function nanmedian>, bin_apply_method='linear', subsample=1.0)

Instantiate a terrain bias correction.

Parameters:

• terrain_attribute (str) – Terrain attribute to use for correction.

• fit_or_bin (Union[Literal['bin_and_fit'], Literal['fit'], Literal['bin']]) – Whether to fit or bin, or both. Use “fit” to correct by optimizing a function or “bin” to correct with a statistic of central tendency in defined bins, or “bin_and_fit” to perform a fit on the binned statistics.

• fit_func (Union[Callable[..., ndarray[Any, dtype[floating[Any]]]], Literal['norder_polynomial'], Literal['nfreq_sumsin']]) – Function to fit to the bias with variables later passed in .fit().

• fit_optimizer (Callable[..., tuple[ndarray[Any, dtype[floating[Any]]], Any]]) – Optimizer to minimize the function.

• bin_sizes (int | dict[str, Union[int, Iterable[float]]]) – Size (if integer) or edges (if iterable) for binning variables later passed in .fit().

• bin_statistic (Callable[[ndarray[Any, dtype[floating[Any]]]], floating[Any]]) – Statistic of central tendency (e.g., mean) to apply during the binning.

• bin_apply_method (Union[Literal['linear'], Literal['per_bin']]) – Method to correct with the binned statistics, either “linear” to interpolate linearly between bins, or “per_bin” to apply the statistic for each bin.

• subsample (float | int) – Subsample the input for speed-up. <1 is parsed as a fraction. >1 is a pixel count.

Methods

__init__([terrain_attribute, fit_or_bin, ...])	Instantiate a terrain bias correction.
apply(elev[, bias_vars, resample, ...])	Apply the estimated transform to a DEM.
copy()	Return an identical copy of the class.
error(reference_elev, to_be_aligned_elev[, ...])	Calculate the error of a coregistration approach.
fit(reference_elev, to_be_aligned_elev[, ...])	Estimate the coregistration transform on the given DEMs.
fit_and_apply(reference_elev, to_be_aligned_elev)	Estimate and apply the coregistration to a pair of elevation data.
info([as_str])	Summarize information about this coregistration.
residuals(reference_elev, to_be_aligned_elev)	Calculate the residual offsets (the difference) between two DEMs after applying the transformation.

Attributes

is_affine	Check if the transform be explained by a 3D affine transform.
is_translation
meta	Metadata dictionary of the coregistration.