Std* (Texture Direction)

Std* (Texture Direction) | Area Roughness Parameters

surface texture parameters in ISO 25178

Height

Spatial

Hybrid

Functional

Functional volume

Feature

The value[s] for Std* is the angle with which the angular spectrum fAPS(S) is the largest. It represents the lay of the surface texture.

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Height	Sa (arithmetical mean height)
Sz (Maximum height)
Sq (Root mean square height)
Ssk (Skewness)
Sku (Kurtosis)
Sp (Maximum peak height)
Sv (Maximum pit height)
Spatial	Sal (Auto-correlation length) / Str (Texture aspect ratio)
Std* (Texture direction)
Hybrid	Sdq (Root mean square gradient)
Sdr (Developed interfacial area ratio)
Functional	Smr(c) Areal material (bearing area) ratio
Smc(mr) Inverse areal material ratio
Sk(Core height)
Spk (Reduced peak height)
Svk (reduced dale height (reduced valley depth))
Smr (Peak material portion)
Smr2 (Valley material portion)
Sxp (Peak extreme height)
Functional volume	Vvv (Dale void volume)
Vvc (Core void volume)
Vmp (Peak material volume)
Vmc (Core material volume)
Feature	Spd (Density of peaks)
Spc (Arithmetic mean peak curvature)
S10z / S5p / S5v / Sda(c) / Sha(c) / Sdv(c) / Shv(c)

Height

Sa (arithmetical mean height)

Sz (Maximum height)

Sq (Root mean square height)

Ssk (Skewness)

Sku (Kurtosis)

Sp (Maximum peak height)

Sv (Maximum pit height)

Spatial

Std* (Texture direction)

Hybrid

Sdq (Root mean square gradient)

Sdr (Developed interfacial area ratio)

Functional

Smc(mr) Inverse areal material ratio

Sk(Core height)

Spk (Reduced peak height)

Smr (Peak material portion)

Smr2 (Valley material portion)

Sxp (Peak extreme height)

Functional volume

Vvv (Dale void volume)

Vvc (Core void volume)

Vmp (Peak material volume)

Vmc (Core material volume)

Feature

Spd (Density of peaks)

Spc (Arithmetic mean peak curvature)