Decimal degrees, DMS or Plus Code: which do you need?

The latitude and longitude finder writes every place in decimal degrees, latitude first: Lisbon is 38.72509, -9.1498. A form or a GPS unit may ask for DMS (degrees, minutes, seconds), DDM (degrees and decimal minutes) or a Plus Code instead.

Which do you need? Decimal degrees, mostly: mapping software and map search boxes read the pair as it is. Write DMS or DDM only when the place you paste into asks for them.

Each conversion by hand is a chance to drop a minus sign, which moves the point to the other side of the equator or of the Greenwich meridian.

How do I read the pair the finder gives?

Latitude comes first, then longitude, each a number of degrees with a sign: positive is north or east, negative is south or west. Lisbon’s 38.72509, -9.1498 is 38.7 degrees north of the equator and 9.1 degrees west of Greenwich.

The finder shows up to five decimals, with a point as the decimal separator. The copy button beside each row copies the pair exactly as shown.

How many decimal places do I need?

Four, for most uses: four decimals place a point within about 11 metres, and Wikipedia’s article on decimal degrees calls four places usually sufficient for most locations. Each extra decimal divides the distance by ten.

East–west, a decimal of longitude covers less ground away from the equator. At 45 degrees of latitude, the same Wikipedia table gives 7.87 m for four decimals of longitude, against 11.1 m.

The finder’s five decimals do not make a town’s coordinate accurate to the metre. Each row gives one point for the whole town, so the decimals locate that point, not a door. “Use my position” rounds your own position to four decimals.

Where does the finder give DMS, DDM or a Plus Code?

In the card “The top match in seven notations”, under the results table. It writes the place of the first row in decimal degrees, DMS, DDM, UTM, MGRS, Plus Code and geohash, each with its copy button.

A Plus Code is a short code for a place without a street address, easy to send in a message. UTM and MGRS are grid positions in metres, used on topographic and military maps.

The card covers the top match only. For another row, work out DMS and DDM from its decimal pair. Keep the whole degrees and multiply the decimal part by 60 for the minutes, then the decimal part of the minutes by 60 for the seconds. The sign becomes N or S, E or W.

Lisbon’s 38.72509 gives 0.72509 × 60 = 43.505 minutes, written 38°43.51′N in DDM. Then 0.505 × 60 = 30.3 seconds, so 38°43′30″N in DMS. Its -9.1498 becomes 9°08.99′W, then 9°08′59″W.

Further down, the “Antipode of the top match” card lists the same seven notations for the point on the opposite side of the Earth. For Lisbon it reads 38°43′30″S 170°51′01″E: do not copy it for the place itself.

How do I put a DMS pair into the finder?

Convert it to decimal degrees first, because Latitude, Longitude and “Distance to” take decimal degrees only. Divide the minutes by 60 and the seconds by 3,600, add both to the degrees, and put a minus sign before a south latitude or a west longitude.

Typed as it stands, 38°43′30″N 9°08′59″W in “Distance to” gets “No place found for the destination”. Converted, 38 + 43/60 + 30/3,600 gives 38.725, and the longitude gives -9.1497: a pair the field accepts.

Questions

Which coordinate format does Google Maps take?

All three: its help page gives examples in decimal degrees, DMS and degrees with decimal minutes, which it calls DMM. For decimal degrees it asks for latitude first and a decimal point rather than a comma, which is how the finder writes its pairs.

Why does the finder show -10 and not -10.00000?

It drops trailing zeros, so -10 is exact to the fifth decimal like every other value on the page. Mbekenyera, in Tanzania, reads -10, 38.98333 for that reason.

Can I look up a place by northing and easting?

Not directly: the finder’s Latitude and Longitude fields take decimal degrees. Convert a UTM or national-grid position to latitude and longitude first, then paste it in.

Sources and further reading

• Decimal degrees — the sign convention, the conversion formula and the table of what each decimal place covers.
• Google Maps Help: find and enter coordinates — the three formats its search box accepts, latitude first, decimal point.
• Plus Codes — what a Plus Code is, and how to read one off Google Maps.