Antenna Height Slant to Vertical Converter
Converts a GNSS slant antenna height measurement to true vertical height using the antenna radius offset.
Inputs
Reduce a slant antenna height to the ARP height with a signed offset — or find the slant to measure.
Enter the values and press Calculate.
Or load an example to see a worked result.
Batch from CSV
One row per calculation, with a header row. Values use the units currently selected in the form above. Up to 10,000 rows; nothing is uploaded.
How the method works
Fixed example values for illustration — not your result.
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
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 radius to that mark and the signed vertical offset from the mark to the antenna reference point (ARP), both from its calibration sheet.
- Read the ARP height — or switch to reverse to find the slant height to tape for a required ARP height.
- Record the antenna model and calibration reference. Under More options, optional standard uncertainties of s, r and o give a first-order uncertainty of the ARP height (refused when the slant is too close to the radius). The batch CSV run carries the antenna reference into its export.
How it works
The slant tape is the hypotenuse of a right triangle whose base is the antenna radius, so the vertical part is √(slant² − radius²).
ARP height = that vertical + the offset, where the offset is positive when the ARP sits above the slant mark and negative when below. Reverse: slant = √((ARP − offset)² + radius²).
The ARP is a physical point; the antenna phase centre is not the ARP, and phase-centre corrections are separate — this tool does not apply them.
Worked example
Slant 1.532 m, radius 0.0921 m. Vertical = √(1.532² − 0.0921²) ≈ 1.529229 m before the offset. A 5 m slant at a 3 m radius gives exactly 4 m; an offset of +0.1 m makes it 4.1 m.
Common mistakes
- Taking the radius and offset from a different antenna model.
- Getting the offset sign backwards — check whether the ARP is above or below the slant mark.
- Recording the slant height as if it were the vertical height.
Tips
- A wrong antenna height feeds straight into your ellipsoidal and orthometric heights — record the antenna model, the mark you measured to and the offset sign.
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 for your exact model, noting which reference point they refer to. A wrong model's values give 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.
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Cite this tool
Zerdly. (2026). Antenna Height Slant to Vertical Converter. Retrieved from https://www.zerdly.com/tools/antenna-height-slant-vertical-converter/
Tip: Enter any known values to calculate the remaining results.
Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.