ZULU Field

EFG technologies

About this app

ZULU Field is the phone companion of the ZULU watch faces for Garmin Instinct: an offline topographic map with a real MGRS grid and military light data, built for use in the field — at night, with gloves, one-handed and without signal.

MGRS GRID ON THE MAP
• A true UTM/MGRS grid drawn over the map, not a latitude/longitude graticule. The spacing follows your zoom: grid zone (54S), 100 km squares (UE), 10 km, 1 km and 100 m lines.
• Grid lines are cut at UTM zone boundaries, as on a printed military map.
• Principal digits (the "88" and "49" of 54S UE 8843 4929) are printed along the top and left edges, large, like the grid numbers on a paper map sheet.
• A crosshair in the centre reads out the MGRS reference of the point under it, principal digits large. Long-press anywhere to move the target there.
• Your own position is shown separately with its MGRS reference, accuracy and the age of the fix. If there is no fix, it says NO POS — it never shows an old position as if it were current.

LIGHT DATA FOR ANY POINT AND DATE
Tap the readout for the light data of the target point or your own position:
• BMNT, sunrise, sunset, EENT
• Moonrise, moonset, moon illumination and phase
• NVG window: when the moon is at least 30° high and at least 23% illuminated
• Period of darkness: the longest stretch between EENT and BMNT with no moon up
• NEXT event with a countdown
Step day by day to plan tonight or next week. Times are 24-hour, in the phone's time zone.

SAME NUMBERS AS THE WATCH
The MGRS and astronomy code is the same algorithm as the ZULU watch face, so the same place on the same day gives the same numbers on your wrist and on your phone. The calculations are checked against independent reference implementations.

OFFLINE MAPS
• GSI Standard Map (Japan): topographic map with contour lines, from the Geospatial Information Authority of Japan
• GSI Aerial Photo (Japan)
• OpenFreeMap (worldwide vector map from OpenStreetMap data; no contour lines yet)
• Download the visible area for a chosen zoom range. You see the tile count and approximate size before you start. Pause, resume and delete downloads.
• The grid, the readout, your position and the light data work with no signal at all.

BUILT FOR THE FIELD
• Dark interface by default, so you keep your eyes adapted at night
• Large buttons (64 dp) at the bottom right, within reach of your thumb, usable with gloves
• Position updates are reduced when the app is not on screen, to save battery
• No Google Play services required

PRIVACY
No account. No ads. No analytics. No tracking. Your location is used only on your phone and is never sent anywhere. Like any online map, map tiles are requested from the map provider (GSI or OpenFreeMap) for the area you view; downloaded areas are stored on your phone.

Not affiliated with, or endorsed by, any military or government agency. Map data: Geospatial Information Authority of Japan (GSI); © OpenFreeMap © OpenMapTiles © OpenStreetMap contributors. Garmin and Instinct are trademarks of Garmin Ltd.; ZULU Field is an independent app and is not made or endorsed by Garmin.

Always carry a paper map and compass. Do not rely on a single device for navigation where safety depends on it.

What’s new

First release: offline GSI and OpenFreeMap maps, MGRS grid with principal digits, crosshair and own-position readouts, light data (BMNT/SR/SS/EENT, moonrise/set, illumination, NVG window, period of darkness) and offline area downloads.