UK Grid Reference Finder

Surveyor.DEV

About this app

Turn your GPS position into a British National Grid reference, and convert between every coordinate system used in Britain and Ireland. It all works offline, on the phone, with no signal at all.

Free. No ads. No accounts. No tracking.

GRID REFERENCE FINDER, POSTCODE FINDER, COORDINATE CONVERTER

Your position, in every format at once:

• OS National Grid reference, 2 to 10 figures
• OSGB36 easting and northing
• WGS84 latitude and longitude, in decimal degrees, degrees and minutes, or degrees minutes seconds
• MGRS, the system used by NATO and mountain rescue
• Plus Codes (Open Location Code), as used by Google Maps
• Irish Grid reference, and Irish Grid easting and northing
• UK postcode

Every one works both ways, and anything the app shows you, you can type back in: with N/S/E/W at either end, a plus or minus, or neither. Paste a pair from a spreadsheet or a message and it splits itself into the right fields.

Show only the cards you use, drag them into the order you want, set the precision of each, and tap and hold any value to copy it.

WHY IT IS ACCURATE

Most apps convert with a 7 parameter Helmert transformation, which is good to roughly 5 metres across Great Britain.

This one uses Ordnance Survey's own OSTN15 model, built into the app rather than downloaded:

• 0.15 m horizontal accuracy at 95%, and 0.148 m measured against OS's own published test points
• Proper OSGB36 values, not an approximation
• True 10 figure grid reference precision

The Irish Grid uses the official OSi and Land and Property Services polynomial. Each card says which transformation it used and how accurate it is, so you are never guessing.

A COMPASS THAT MATCHES YOUR MAP

Most compass apps show magnetic north and leave the corrections to you. This one shows all three norths at once:

• Magnetic, what the sensor reads
• True, corrected using the World Magnetic Model from your position
• Grid, the north your OS map is drawn against, using the exact grid convergence where you are standing

Tap the dial to mark a bearing; the app shows how far you have turned and which way to turn back, in whole circle or quadrant notation. A spirit level shows when the phone is flat enough to trust the reading, and your GPS course cross checks the sensor while you walk.

POSTCODE FINDER, ONLINE AND OFFLINE

Postcodes come from postcodes.io when you have a connection. With no signal the app falls back to the device geocoder, so you still get an answer in the field.

IN YOUR OWN LANGUAGE

Fourteen languages: English, Welsh, Irish, French, Spanish, Portuguese, German, Dutch, Italian, Polish, Romanian, Ukrainian, Japanese and Chinese. Every screen, not just the menus, with the surveying terms translated as surveying terms.

PHONES AND TABLETS, EITHER WAY UP

Turn the device and the layout follows. Sideways your cards sit in two columns; on a tablet, three, with every readout on screen at once. Lock it to portrait or landscape if you would rather it stayed put, for a dashboard or handlebar mount.

MADE FOR FIELD USE

• Works offline, indoors or outdoors
• Left or right handed button placement
• Dark mode, haptic feedback, adjustable GPS rate
• A setup guide the first time you open it, and a guided tour any time
• Share your position as text, open it in your maps app, or open it on the MapGrid web map with a named marker

Built for hillwalkers, mountain rescue, surveyors, ecologists, GIS and archaeology professionals, geocaching, hiking and anyone who has ever read a six figure grid reference over a radio.

If you are looking for a UK grid reference finder with postcode lookup and high precision conversion between WGS84, OSGB36 and the British National Grid, this is the one.

Uses OSTN15/OSGM15 and the OSi/LPS polynomial (c) Ordnance Survey Ltd, Land & Property Services and Ordnance Survey Ireland, under the BSD licence. True north via the World Magnetic Model (NOAA/NCEI and BGS). Postcodes from postcodes.io.

What’s new

🆕 New since 2.1.1:
• New Compass tab: magnetic, true and grid north at once
• New cards: MGRS, Plus Codes and the Irish Grid
• Landscape and tablet layouts, with cards in two or three columns
• Now in 14 languages
• Settings rebuilt, plus a setup guide the first time you open it

🐛 Fixes:
• Manual input now accepts every format the app can display
• Fixed tablets sometimes never finding a position
• Fixed the compass reading 360° instead of 0°