Antenna Height Slant to Vertical Converter
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
Enter Values
How to use this calculator
- Enter the slant height you taped from the ground mark to the antenna's slant measurement mark.
- Enter the antenna's slant radius from its data sheet.
- Add the vertical offset to the antenna reference point (ARP) if the data sheet gives one, then read the true vertical height.
How it works
A slant tape measures the sloping distance to a mark on the antenna's edge, so the true vertical height is √(slant² − radius²) by Pythagoras, using the antenna's slant radius.
You then add the vertical offset from that mark to the antenna reference point (ARP) so the height matches the point your GNSS processing expects.
Worked example
Slant 1.532 m, radius 0.0921 m. Vertical = √(1.532² − 0.0921²) ≈ 1.529 m, plus any ARP offset from the antenna calibration sheet.
Tips
- A wrong antenna height feeds straight into your ellipsoidal and orthometric heights — double-check the radius, offset and the mark you measured to.
Frequently asked questions
Why not just measure vertically?
A vertical tape to the antenna edge is awkward and easy to get wrong over a tripod. A slant measurement to a defined mark is repeatable; the geometry then converts it to the vertical height.
Where do the radius and offset come from?
From the antenna manufacturer's calibration/data sheet (or the IGS antenna tables). Using the wrong antenna model's values is a common source of a constant height error.
Is this official course material?
No. It is free study support mapped to surveying course levels — not official North Metropolitan TAFE content or advice. Always follow your lecturer and the official assessment brief, and check your own working.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.