focal_metrics: Calculate Texture Metrics per Pixel

In geodiv: Methods for Calculating Gradient Surface Metrics

Calculate Texture Metrics per Pixel

Description

Calculates the various texture metrics over windows centered on individual pixels. This creates a continuous surface of the texture metric. This function is a modified version of the window_lsm function from the landscapemetrics package (Hesselbarth et al. 2019).

Usage

focal_metrics(x, window, metrics, progress, ...)

Arguments

x	A raster or matrix. Image over which to apply focal window calculations.
window	Matrix. The focal window used to create the image.
metrics	List. List of metrics to apply. Function names must be strings.
progress	Logical. Display progress through metrics list?
...	Additional arguments for the metric functions. All applicable arguments will be applied to the entire list of metrics.

Details

Metrics available from geodiv package:

1. 'sa': average surface roughness

2. 'sq': root mean square roughness

3. 's10z': ten-point height

4. 'sdq': root mean square slope of surface, 2-point method

5. 'sdq6': root mean square slope of surface, 7-point method

6. 'sdr': surface area ratio

7. 'sbi': surface bearing index

8. 'sci': core fluid retention index

9. 'ssk': skewness

10. 'sku': kurtosis

11. 'sds': summit density

12. 'sfd': 3d fractal dimension

13. 'srw': dominant radial wavelength, radial wavelength index, mean half wavelength

14. 'std': angle of dominating texture, texture direction index

15. 'svi': valley fluid retention index

16. 'stxr': texture aspect ratio

17. 'ssc': mean summit curvature

18. 'sv': maximum valley depth

19. 'sph': maximum peak height

20. 'sk': core roughness depth

21. 'smean': mean peak height

22. 'svk': reduced valley depth

23. 'spk': reduced peak height

24. 'scl': correlation length

25. 'sdc': bearing area curve height interval

Value

A raster of the metric calculated in windows over the raster or matrix. If the input was a matrix, the function will return a raster with an extent of [0, 1, 0, 1].

References

1. Hesselbarth, M.H.K., Sciaini, M., With, K.A., Wiegand, K., Nowosad, J. 2019. landscapemetrics: an open-source R tool to calculate landscape metrics. - Ecography 42:1648-1657(ver. 0).

Examples

# import raster image
data(normforest)
normforest <- terra::unwrap(normforest)

# crop raster to smaller area
x <- terra::crop(normforest, terra::ext(normforest[1:100, 1:100, drop = FALSE]))

# get a surface of root mean square roughness
sa_img <- focal_metrics(x = x, window = matrix(1, 5, 5),
                        metrics = list('sa'), progress = TRUE)

# plot the result
terra::plot(sa_img$sa)

geodiv documentation built on Oct. 6, 2023, 1:07 a.m.