Coordinate converter: decimal degrees, DMS and UTM (WGS84, ETRS89 and ED50)

What this converter does

It converts a position between the three ways a coordinate is written: decimal degrees (43.0097, −7.5560), degrees, minutes and seconds (43° 0′ 34.92″ N, 7° 33′ 21.60″ W) and UTM (zone 29T, X 617 680 m, Y 4 762 904 m). It also gives the degrees and decimal minutes used by GPS units and nautical charts, the point’s scale factor and meridian convergence, and links to open it in Google Maps, Waze, Apple Maps or OpenStreetMap.

It also changes datum: you can enter in ED50 and get ETRS89, or the reverse. That is what it takes to place a substation, a tower or an earth electrode from a thirty-year-old project onto current mapping.

Accepted formats

Latitude and longitude can be typed as they come. In decimal, with a minus sign for south and west; in degrees, minutes and seconds, with or without the symbols and with the hemisphere letter: “43° 0′ 34.9″ N”, “43 0 34.9 N”, “N 43 0 34.9” and “43d0m34.9s” all give the same result. If they are entered the wrong way round — longitude in the latitude box — the converter spots it from the letters and swaps them.

In UTM, the zone can go on its own (30) or with its band letter (30T); with the letter, the hemisphere is taken from it.

Google Maps, Waze and Apple Maps links

In the “Map link” tab you paste the link any of the three apps gives you, or an Android geo: URI, and the converter extracts the position. From Google Maps it reads a place’s marked point (the !3d and !4d values in the link) before the view centre (@lat,lon), because that is the point that was chosen; if there is only a centre, it says so. From Waze it reads links with ll= and shared links of the waze.com/ul/h… type, which carry the position as a geohash. From Apple Maps, the ll, q, daddr and coordinate parameters.

Short links — maps.app.goo.gl, goo.gl/maps, maps.apple/p — do not carry the coordinates: they are a redirect that only resolves when opened, and the converter sends nothing to any server to follow it. Just open them and copy the long address that appears.

On output, the converter gives the point as a Google Maps, Waze, Apple Maps and OpenStreetMap link, each with a copy button: the quick way to send a technician the location of a substation that the project gave in UTM and ED50.

UTM zones and bands

UTM divides the Earth into 60 zones of 6° longitude and projects each with a transverse Mercator of scale factor 0.9996 on the central meridian. X carries a false easting of 500 000 m so it is never negative, and in the southern hemisphere Y carries a false northing of 10 000 000 m. The converter picks each point’s natural zone, including the Norway and Svalbard exceptions, but another can be forced: it is common to keep a whole project in one zone rather than split it. Outside its zone distortion grows quickly, and the converter warns about it.

The calculation uses the Krüger series from the NGA definition of UTM, with an error below one millimetre within the zone. UTM runs from 80° S to 84° N; beyond that the polar stereographic projection (UPS) applies, which this converter does not handle.

WGS84, ETRS89 and ED50

WGS84 is the system of GPS and Google Maps; ETRS89, the European one. They drift apart by about 2.5 cm a year with the Eurasian plate and today differ by less than a metre, so the converter treats them as one.

ED50 is the datum of older European mapping, on the International 1924 ellipsoid. For ED50 to ETRS89 the converter uses the seven parameters published by Spain’s IGN (three translations, three rotations and a scale factor): one set for the mainland and one for the Balearic Islands, with residuals of one to two metres. For points outside Spain there is the European mean three-parameter transformation (EPSG:1133), with an error of five to ten metres. Where centimetre accuracy is needed, the tool is the national NTv2 grid.

Worked example

A point in Lugo (Spain) from Google Maps: 43.0097, −7.5560. In degrees, minutes and seconds it is 43° 0′ 34.92″ N, 7° 33′ 21.60″ W, and in degrees and decimal minutes 43° 0.5820′ N, 7° 33.3600′ W. In UTM on ETRS89 it falls in zone 29T, with X = 617 680.43 m and Y = 4 762 903.61 m.

If the same point has to be found on an ED50 drawing, choose ED50 as the output datum: X = 617 800.33 m, Y = 4 763 116.51 m. That is 120 m further east and 213 m further north on paper: the difference that sends a setting-out with mixed coordinates into the next plot.

Forced into zone 30, the same point comes out as X = 128 678.81 m and Y = 4 771 973.34 m, and the converter warns that it is more than 3° from the central meridian.

What this converter does not do

It does not handle heights: neither GPS ellipsoidal height nor orthometric height above sea level, which needs a geoid model. It does not use NTv2 grids, so the ED50–ETRS89 step stays at one or two metres. It does not give MGRS or UPS coordinates. It does not convert other historical datums (OSGB36, NAD27, Datum 73, Roma40, DHDN, NTF) or national projections other than UTM (British National Grid, Lambert, Gauss-Krüger).

What it relates to

The unit converter in this same section converts single angles between decimal degrees, degrees-minutes-seconds, radians and gradians. And the exact position of each electrode is half of a well-documented resistivity survey: the other half is the earth tester readings and the earthing calculator.