velocity_track {QuAnTeTrack}R Documentation

Calculate velocities and relative stride lengths for tracks

Description

velocity_track() calculates the velocities and relative stride lengths for each step in a series of tracks, based on the step length, height at the hip, and gravity acceleration.

Usage

velocity_track(data, H, G = NULL, method = NULL)

Arguments

data

A track R object, which is a list consisting of two elements:

  • Trajectories: A list of interpolated trajectories, where each trajectory is a series of midpoints between consecutive footprints.

  • Footprints: A list of data frames containing footprint coordinates, metadata (e.g., image reference, ID), and a marker indicating whether the footprint is actual or inferred.

H

A numeric vector representing the height at the hip (in meters) for each track maker. The length of this vector should match the number of tracks in the data.

G

Gravity acceleration (in meters per second squared). Default is 9.8.

method

A character vector specifying the method to calculate velocities for each track. Method "A" follows the approach from Alexander (1976), while method "B" is based on Ruiz & Torices (2013). If NULL, method "A" will be used for all tracks.

Details

The velocity_track() function calculates velocities using two methods:

Method A: Based on Alexander (1976), with the formula:

v = 0.25 \cdot \sqrt{G} \cdot S^{1.67} \cdot H^{-1.17}

This method applies to a wide range of terrestrial vertebrates and is used to estimate velocity across different gaits.

Method B: Based on Ruiz & Torices (2013), with the formula:

v = 0.226 \cdot \sqrt{G} \cdot S^{1.67} \cdot H^{-1.17}

Based on Thulborn & Wade (1984), it is possible to identify the gaits of track-makers on the basis of relative stride length, as follows:

Value

A track velocity R object consisting of a list of lists, where each sublist contains the computed parameters for a corresponding track. The parameters included are:

Logo

Logo.png

Author(s)

Humberto G. Ferrón

humberto.ferron@uv.es

Macroevolution and Functional Morphology Research Group (www.macrofun.es)

Cavanilles Institute of Biodiversity and Evolutionary Biology

Calle Catedrático José Beltrán Martínez, nº 2

46980 Paterna - Valencia - Spain

Phone: +34 (9635) 44477

References

Alexander, R. M. (1976). Estimates of speeds of dinosaurs. Nature, 261(5556), 129-130.

Ruiz, J., & Torices, A. (2013). Humans running at stadiums and beaches and the accuracy of speed estimations from fossil trackways. Ichnos, 20(1), 31-35.

Thulborn, R. A., & Wade, M. (1984). Dinosaur trackways in the Winton Formation (mid-Cretaceous) of Queensland. Memoirs of the Queensland Museum, 21(2), 413-517.

See Also

tps_to_track

Examples

# Example 1: Calculate velocities for the MountTom dataset using default settings.
# H_mounttom contains hip heights for each track in the MountTom dataset.
# The function will use the default method "A" for all tracks.
# Hip heights are inferred as four times the footprint length, following Alexander's approach.
H_mounttom <- c(
  1.380, 1.404, 1.320, 1.736, 1.364, 1.432, 1.508, 1.768, 1.600,
  1.848, 1.532, 1.532, 0.760, 1.532, 1.688, 1.620, 0.636, 1.784, 1.676, 1.872,
  1.648, 1.760, 1.612
)
velocity_track(MountTom, H = H_mounttom)

# Example 2: Calculate velocities for the PaluxyRiver dataset using default settings.
# H_paluxyriver contains hip heights for each track in the PaluxyRiver dataset.
# The function will use the default method "A" for all tracks.
# Hip heights are inferred as four times the footprint length, following Alexander's approach.
H_paluxyriver <- c(3.472, 2.200)
velocity_track(PaluxyRiver, H = H_paluxyriver)

# Example 3: Calculate velocities for the PaluxyRiver dataset using different methods
# for velocity calculation. Method "A" is used for sauropods, which is more
# appropriate for quadrupedal dinosaurs. Method "B" is used for theropods, which
# is more appropriate for bipedal dinosaurs. Hip heights are inferred as four times
# the footprint length, following Alexander's approach.
H_paluxyriver <- c(3.472, 2.200)
Method_paluxyriver <- c("A", "B")
velocity_track(PaluxyRiver, H = H_paluxyriver, method = Method_paluxyriver)


[Package QuAnTeTrack version 0.1.0 Index]