Document Holder Angle Neck Flexion Reducer Checker

Compare actual document-center sightline geometries preserving upward/downward sign and worsening changes; sightline is not measured neck flexion or guaranteed neck-load reduction.

Description

A document sightline has a signed downward angle.

A document sightline has a signed downward angle. Raising a document above eye level makes that angle negative.^[1]

Enter nonnegative eye/current/proposed document-center heights and positive current/proposed distances. Return both angles and current minus proposed reduction.

When to use Document Holder Angle Neck Flexion Reducer Checker

Use Document Holder Angle Neck Flexion Reducer Checker when you need to evaluate the supplied records under the calculation and evidence rules below. Sightline angle is not neck flexion; no guaranteed neck-load reduction is inferred.

Prepare measured task, body, furniture or already weighted exposure records. Supply independently verified caller policies, tables and comparison limits with matching units and conditions.

How to use Document Holder Angle Neck Flexion Reducer Checker and understand its results

Prepare measured task, body, furniture or already weighted exposure records. Supply independently verified caller policies, tables and comparison limits with matching units and conditions.
Enter measuredEyeHeightCm, currentDocumentCenterHeightCm, currentDocumentHorizontalDistanceCm, proposedDocumentCenterHeightCm, proposedDocumentHorizontalDistanceCm using the field table and calculation rules, then run the tool.
Read currentDownwardSightlineDegrees, proposedDownwardSightlineDegrees, signedDownwardSightlineReductionDegrees. 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
measuredEyeHeightCm	Measured eye height cm	number	Required
currentDocumentCenterHeightCm	Current document center height cm	number	Required
currentDocumentHorizontalDistanceCm	Current document horizontal distance cm	number	Required
proposedDocumentCenterHeightCm	Proposed document center height cm	number	Required
proposedDocumentHorizontalDistanceCm	Proposed document horizontal distance cm	number	Required

Enter nonnegative eye/current/proposed document-center heights and positive current/proposed distances. Return both angles and current minus proposed reduction.

downwardAngle=atan2(eye−documentHeight,horizontalDistance)

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

Output field	Meaning	Value type
currentDownwardSightlineDegrees	Current downward sightline degrees	number
proposedDownwardSightlineDegrees	Proposed downward sightline degrees	number
signedDownwardSightlineReductionDegrees	Signed downward sightline reduction degrees	number

json

{
  "input": {
    "measuredEyeHeightCm": 120,
    "currentDocumentCenterHeightCm": 90,
    "currentDocumentHorizontalDistanceCm": 50,
    "proposedDocumentCenterHeightCm": 110,
    "proposedDocumentHorizontalDistanceCm": 50
  },
  "output": {
    "currentDownwardSightlineDegrees": 30.96375653207352,
    "proposedDownwardSightlineDegrees": 11.309932474020213,
    "signedDownwardSightlineReductionDegrees": 19.65382405805331
  }
}

Limitations and assumptions

Sightline angle is not neck flexion; no guaranteed neck-load reduction is inferred.

Numeric inputs, where present, must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Monitor Top-at-Eye Height Alignment Checker: Screen-top alignment uses a measured eye datum and signed offset. Caller bounds determine the nearest compatible offset. For a complementary task, use Screen Glare Window Reflection Angle Risk Checker: A planar specular reflection can point toward a viewer. Incoming ray direction differs from a vector pointing toward the window.

References

Document Holder Angle Neck Flexion Reducer Checker — tool.io

Similar or alternative tools

Monitor Top-at-Eye Height Alignment Checker
Screen-top alignment uses a measured eye datum and signed offset. Caller bounds determine the nearest compatible offset.
Screen Glare Window Reflection Angle Risk Checker
A planar specular reflection can point toward a viewer. Incoming ray direction differs from a vector pointing toward the window.