Absolute difference of river length between 1800 and today

Determine the absolute difference in length of the River Elbe comparing the historical river axis from the year 1800 sf.axis1800 and the recent course of the river sf.axis for a specific hectometer and within an adjustable buffer distance. The returned value is the difference in meters. A positive value indicates that the historical axis shortened over time and a positive value indicates that the recent axis is longer than the historical one within the specified area.

Usage

getAxisADiff(x, b, bu = b)

Arguments

x

must be a single integer indexing one hectometer polygon of sf.afe_csa along the River Elbe. x must be element of seq(from = 1, to = length(sf.afe_csa), by = 1).

b

must be a single numeric specifying a buffersize to be included for the axis length computations around the indexed hectometer in m.

bu

is an optional single numeric specifying a separate upstream buffersize to be included for the axis length computations around the indexed hectometer in m (default = b).

Value

numeric with an absolute difference of axis length (1800 to present) in m.

See also

sf.afe_csa, sf.axis, sf.axis1800

Examples

   getAxisADiff(3325, 200)
#> Warning: attribute variables are assumed to be spatially constant throughout all geometries
#> Warning: attribute variables are assumed to be spatially constant throughout all geometries
#> [1] 577.9273
   getAxisADiff(3900, 200)
#> Warning: attribute variables are assumed to be spatially constant throughout all geometries
#> Warning: attribute variables are assumed to be spatially constant throughout all geometries
#> [1] 0.01846505