Apply the opening operation to A with window size ω.

B, flags = pmf(A; ωₘ, slope, dhₘ, dh₀, cellsize)

Applies the progressive morphological filter by [Zhang et al. (2003)] to A.

Output

• B::Array{T,2} Maximum allowable values
• flags::Array{Float64,2} A sized array with window sizes if filtered, zero if not filtered.

Afterwards, one can retrieve the resulting mask for A by A .<= B or flags .== 0..

Arguments

• A::Array{T,2} Input Array
• ωₘ::Float64=20. Maximum window size [m]
• slope::Float64=0.01 Terrain slope [m/m]
• dhₘ::Float64=2.5 Maximum elevation threshold [m]
• dh₀::Float64=0.2 Initial elevation threshold [m]
• cellsize::Float64=1. Cellsize in [m]

[Zhang et al. (2003)] Zhang, Keqi, Shu-Ching Chen, Dean Whitman, Mei-Ling Shyu, Jianhua Yan, and Chengcui Zhang. “A Progressive Morphological Filter for Removing Nonground Measurements from Airborne LIDAR Data.” IEEE Transactions on Geoscience and Remote Sensing 41, no. 4 (2003): 872–82. [https://doi.org/10.1109/TGRS.2003.810682].

image = pssm(A; exaggeration, resolution)

Perceptually Shaded Slope Map by [Pingel, Thomas, and Keith Clarke. 2014].

Output

• image::Gray{T,2} Grayscale image

Arguments

• A::Array{Real,2} Input Array
• exaggeration::Real=2.3 Factor to exaggerate elevation
• resolution::Real=1.0 Resolution of cell size

[Pingel, Thomas, and Keith Clarke. 2014]. ‘Perceptually Shaded Slope Maps for the Visualization of Digital Surface Models’. Cartographica: The International Journal for Geographic Information and Geovisualization 49 (4): 225–40. https://doi.org/10/ggnthv.]

B = smf(A; ω, slope, dhₘ, dh₀, cellsize)

Applies the simple morphological filter by [Pingel et al. (2013)] to A.

Output

• B::Array{Float64,2} A filtered version of A

Arguments

• A::Array{T,2} Input Array
• ω::Float64=18. Maximum window size [m]
• slope::Float64=0.01 Terrain slope [m/m]
• cellsize::Float64=1. Cellsize in [m]

[Pingel et al. (2013)] Pingel, Thomas J., Keith C. Clarke, and William A. McBride. 2013. ‘An Improved Simple Morphological Filter for the Terrain Classification of Airborne LIDAR Data’. ISPRS Journal of Photogrammetry and Remote Sensing 77 (March): 21–30. [https://doi.org/10.1016/j.isprsjprs.2012.12.002].