Input variables
| Variable | Meaning | Unit |
|---|---|---|
| t | Intended test length | mm |
| x | Measured horizontal length | mm |
| y | Measured vertical length | mm |
| z | Current zoom | % |
Equations
Horizontal corrected zoom · %
zx = z*t/x
Vertical corrected zoom · %
zy = z*t/y
Axis mismatch · %
delta = 100*abs(x-y)/((x+y)/2)
Notation
PI means π. ** means a power, sqrt means square root, and abs gives the absolute value. Trigonometric functions use radians. min and max select the smallest or largest argument.
ceil rounds upward, floor rounds downward, and round rounds to the nearest integer with halves toward positive infinity. roundup(value, step) rounds upward to the next multiple of the step; a zero step leaves the value unchanged.
Assumptions
- Measure a test square on the cutting surface, not the wall or projector housing.
- Different horizontal and vertical corrections suggest tilt, keystone or aspect-ratio distortion. One uniform zoom cannot fix both.
- Disable fit-to-page scaling and check several positions across the projection.
- Recheck calibration after moving the table, projector or cutting mat.
Precision and verification
The tool uses ordinary double-precision numeric arithmetic. Output is displayed to at most four decimal places; measurement precision is usually much lower. Check the worked examples, your project’s specifications, and a real sample before committing material.