Alexander Footprint Speed Estimator

Evaluate Alexander’s published footprint-stride speed approximation with explicit estimated hip height; stride is successive same-foot spacing, not step length, and model does not prove gait or actual speed.

Description

Footprint stride is the spacing of successive prints from the same foot.

Footprint stride is the spacing of successive prints from the same foot. Alexander's empirical speed relation also needs an estimated hip height.

When to use Alexander Footprint Speed Estimator

Use this tool to evaluate Alexander’s published footprint-stride speed approximation with explicit estimated hip height; stride is successive same-foot spacing, not step length, and model does not prove gait or actual speed.

Prepare the fossil measurements or occurrence records and the chosen calibration parameters. Retain the stated coordinate, age and measurement conventions.

How to use Alexander Footprint Speed Estimator and understand its results

Prepare the fossil measurements or occurrence records and the chosen calibration parameters. Retain the stated coordinate, age and measurement conventions.
Enter measuredStrideLengthM, estimatedHipHeightM, gravityMPerSecondSquared using the field table and calculation rules, then run the tool.
Read alexanderModelSpeedMPerSecond, dimensionlessStrideLength. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
measuredStrideLengthM	Measured stride length m	number	Required
estimatedHipHeightM	Estimated hip height m	number	Required
gravityMPerSecondSquared	Gravity m per second squared	number	Required

Use positive stride and hip height in meters and positive gravity. Return model m/s and stride/hip-height ratio.^[1]

speed = 0.25 × sqrt(gravity) × stride^1.67 × hip height^(−1.17)

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
alexanderModelSpeedMPerSecond	Alexander model speed m per second	number
dimensionlessStrideLength	Dimensionless stride length	number

json

{
  "input": {
    "measuredStrideLengthM": 2,
    "estimatedHipHeightM": 1,
    "gravityMPerSecondSquared": 1
  },
  "output": {
    "alexanderModelSpeedMPerSecond": 0.7955364837549186,
    "dimensionlessStrideLength": 2
  }
}

Limitations and assumptions

Do not substitute step length; the approximation does not establish actual speed or gait.

Numbers and computed results must be finite; overflow produces an error. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Trackway Gait Transition Speed Threshold: Propagate caller hip-height and transition-Froude bounds into threshold-speed scenarios and compare a supplied track speed; not the existing simple Froude calculation or a universal walking/running determination. For a complementary task, use Hydraulic Equivalence Settling Velocity: Invert measured fossil settling speed to a Stokes-equivalent reference sediment diameter and applicability Reynolds screen; unlike existing forward Stokes particle settling, the target is equivalent grain size, with non-creeping estimates flagged.

References

Alexander Footprint Speed Estimator — tool.io

Similar or alternative tools

Trackway Gait Transition Speed Threshold
Propagate caller hip-height and transition-Froude bounds into threshold-speed scenarios and compare a supplied track speed; not the existing simple Froude calculation or a universal walking/running determination.
Hydraulic Equivalence Settling Velocity
Invert measured fossil settling speed to a Stokes-equivalent reference sediment diameter and applicability Reynolds screen; unlike existing forward Stokes particle settling, the target is equivalent grain size, with non-creeping estimates flagged.