User guide

Figure-8 calibration

When the app reports low accuracy or the needle looks off:

1. Move about 1 m away from metal, magnets, speakers and electronics.
2. Hold the phone and draw a figure 8 in the air 3-5 times, flipping the phone as you go.
3. Wait for the accuracy indicator to turn green.

True vs magnetic north

Magnetic north is where a magnetic needle points; true north points to the geographic North Pole and matches maps. In Vietnam the difference is under 1 degree, but elsewhere it can exceed 10 degrees. The app shows true north by default, computed with the WMM model from your location and date.

Magnetic interference

Earth's field is about 25-65 µT. Outside that range the app warns you: remove magnetic cases, step away from cars and steel beams, and try again.

Location permission

Location is only needed for true north, coordinates and navigation. The app asks when you use those features, preferring approximate location while in use.

1. Choose "Only while using the app".
2. You may pick "Approximate location" - true north stays accurate.
3. Declining still lets you use the magnetic compass.

Reading the compass

Hold the phone flat with the top pointing where you want to measure. The number in the middle is the heading of the top edge: 0° North, 90° East, 180° South, 270° West.

Safe mode

After repeated crashes the app opens in safe mode with core features so you can still use the compass and export data. Updating to a new version exits safe mode automatically.