Zerdly

Map Bearing Romer Tool

A compass rose for whole-circle, quadrant and back bearings, with north-reference conversion and a printable, calibrated romer.

100% FreeRuns in your browserBasic
How to use this calculator

Bearing

Sign

Whole-circle bearing, clockwise from north. Conventions: true = grid + γ (γ clockwise from true to grid north); true = magnetic + δ (δ east positive). No declination is looked up — enter your own from a dated model.

NESW

Solid: forward bearing · dashed: back bearing

Forward bearing
45°
Back bearing
225°
Quadrant bearing
N 45.0000° E
True bearing
Needs γ
Grid bearing
45°
Magnetic bearing
Needs γ and δ

Map overlay (optional)

Lay the bearing over your own map image. The image stays in this browser tab — it is not uploaded or saved, and it is released when you change or clear it.

Map scale and printable romer

= 40 mm on the map

Romer 1:25000 — 1 km square = 40.0 mm, ticks every 100 mCalibration: this line must measure exactly 100 mm. Print at 100% (actual size), not "fit to page".

Print at 100% (actual size), never “fit to page”, then measure the calibration line: it must be exactly 100 mm. The tool cannot see your printer, so only your ruler can confirm the scale.

How the method works

A fixed worked example to explain the method — it is not your result.

Whole-circle azimuth is clockwise from north
Illustrative method
Whole-circle azimuth is clockwise from northCompass rose with N, E, S and W, the forward bearing as a solid arrow, the back bearing dashed and the quadrant angle shaded from the nearer of north or south.NESWAzimuth 135°S 45° EBack 315° (dashed)
Whole-circle azimuth is measured clockwise from north (0–360°). 135° azimuth = S 45° E; back azimuth = 315°.

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

  1. Enter a whole-circle bearing in DD, DMS or DDM — or drag on the compass rose, or focus it and use the arrow keys (Shift for 10°). Use the − sign for an anticlockwise value; −10° becomes 350°.
  2. Say whether the bearing is from grid, true or magnetic north, and enter the grid convergence and/or magnetic declination if you have them.
  3. Read the forward, back and quadrant bearings, and the bearing in each north reference your corrections allow.
  4. Enter the map scale to convert ground distances to map millimetres, then print or download the romer and check its 100 mm calibration line with a ruler.
  5. Optionally open your own map image: set the bearing origin to see the bearing drawn on it, click two points to measure a bearing, and calibrate the scale from two points and a distance you type. The image stays in the browser — it is never uploaded.

How it works

Whole-circle bearings run clockwise from north (0–360°); the back bearing is the forward bearing + 180°. The quadrant form follows the same rules as the azimuth-to-bearing converter (135° = S 45° E).

North references use printed conventions: true = grid + γ (γ clockwise from true to grid north) and true = magnetic + δ (δ positive east). No declination is looked up or guessed — a conversion that needs one says so until you enter it from a dated model.

Map length = ground distance ÷ scale: at 1:25 000, 1 km is 40 mm, and the romer's 100 m ticks are 4 mm apart.

The printable romer is drawn in real millimetres. Print it at 100% (actual size) and measure the calibration line: only your ruler can confirm the printer did not rescale it.

Worked example

135° grid bearing at 1:25 000. Quadrant S 45° E, back bearing 315°. With γ = +0.6° the true bearing is 135.6°. A 1 km leg measures 40 mm on the map.

Common mistakes

  • Printing with 'fit to page' on — the romer is then the wrong size. Measure the calibration line every time.
  • Applying declination with the wrong sign: east declination is positive here, so true = magnetic + δ.
  • Treating the on-screen rose as a precise instrument; it is a bearing aid, and the numbers are the result.

Frequently asked questions

What's a back bearing?

The bearing looking the opposite way along the same line — the forward bearing plus or minus 180°. It's used to check and to set out the reverse direction.

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). Map Bearing Romer Tool. Retrieved from https://www.zerdly.com/tools/map-bearing-romer-tool/

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.