Acoustic target calibration: step by step to the millimetre

When we say accuracy of “about 2 mm”, we mean after calibration. Without it, the coordinates in the app almost always sit slightly off from the real holes. That sounds like a drawback, but in practice it is 5–10 minutes of one-off setup, after which the system lands exactly on the point. Here is why it is needed and how to do it.

Why coordinates drift without calibration

Any target, once installed, stands at a microscopic tilt or rotation relative to the line of fire — setting it up perfectly by eye is impossible. For the system that turns into a small systematic offset: every point in the app shifts a couple of millimetres in the same direction. Calibration simply enters a correction for that offset.

This is not a defect, and not something specific to our system — it is how any precise acoustic registration works. So treat calibration not as a workaround but as a normal installation step, the same as levelling the target.

When you need it

• On the first installation at a new location.
• After reinstalling or significantly moving the target.
• Before every session at an already-configured spot — not needed.

What you will need

• The target installed per the manual (frame square to the direction of fire).
• A phone with the Sekundant app.
• A tape measure or ruler — for the precise mode.
• At least three sighting shots.

Calibration step by step

1. Install the target per the manual, as square as you can. The tidier the installation, the smaller the correction.
2. From the firing position, take at least three sighting shots.
3. Walk up to the target and compare the real holes with the points in the app — there is almost always a small difference.
4. Start calibration in the app and choose the mode — quick or precise (see below).

Two modes: quick and precise

The app offers two ways to calibrate, for different tasks:

Simplified — “manual match-up”

On the phone screen you drag the group of recorded shots until it lines up with the real holes in the target. Fast and visual, but the accuracy depends on your eye — not enough for millimetre work. A good option for dynamic shooting, where speed matters more than absolute precision.

Precise — “by shots”

Here you measure the coordinates of each shot from the centre of the target with a tape — along the X and Y axes — plus the scale factor (the maximum distance between the outermost shots in the group). Those values are entered into the app by hand. It takes a little longer, but this is the mode that delivers the stated millimetre accuracy. It is the one to use for zeroing and precision shooting.

What accuracy to expect after calibration

These are average errors across a string, not a laboratory maximum (in ideal conditions the system goes down to 1 mm):

• Akustik — about 2 mm;
• Gorizont — about 5 mm;
• Gorizont Mini — about 7 mm.

Without calibration those figures are out of reach — so if accuracy matters to you, spend a few minutes on setup at the first installation.

In short

• Calibration is a normal installation step, not a workaround. It takes 5–10 minutes.
• Needed at the first installation at a new location and after reinstalling.
• Simplified mode — fast, by eye; precise mode (“by shots”) — for millimetre accuracy.
• The stated ~2 / 5 / 7 mm are figures after calibration.