Coordinate Converter, WGS84, UTM, ITRF, ED50

Understanding Coordinate Systems

The same point on Earth can be described by very different sets of numbers depending on the coordinate reference system (CRS) you use. A CRS defines two things: a datum (the model of the Earth's shape and where it is anchored) and, often, a projection (how the curved surface is flattened onto a map). Mixing systems without converting is one of the most common sources of error in GIS work, points can land hundreds of metres away from where they belong. Below are the systems this converter handles most often.

WGS84, The GPS Standard

WGS84 (EPSG:4326) is the global datum behind GPS, smartphones, and almost every web map. Its coordinates are geographic, plain latitude and longitude in decimal degrees, for example 41.0082, 28.9784 for Istanbul. If your data came from a phone, a GPS receiver, or an online map, it is almost certainly WGS84. Use it whenever you need a single, worldwide reference that everyone understands.

UTM, Metres Instead of Degrees

The Universal Transverse Mercator system slices the globe into narrow north–south zones and projects each one separately, so positions are expressed in metres (easting and northing) rather than degrees. This makes distance and area calculations straightforward, which is why surveyors and engineers prefer it. Turkey falls in 6-degree UTM zones 35–38 (and in finer 3-degree zones for cadastral work). You pick UTM when you need to measure on the ground, not just locate on a globe.

ED50, Legacy European Maps

ED50 (European Datum 1950) is an older datum still embedded in many historical Turkish and European maps, cadastral records, and infrastructure plans. Because it is anchored differently from WGS84, the same coordinates sit about 100–130 metres off in Türkiye (about 150–190 metres in Spain) if you treat ED50 data as WGS84. Whenever you combine archival maps with modern GPS data, a correct ED50 ↔ WGS84 conversion is essential, and the best parameters depend on the country.

ITRF96, High-Precision Modern Geodesy

ITRF96 is the high-accuracy reference frame underlying Turkey's national TUREF system. For everyday GIS it can be treated as WGS84, although TUREF coordinates refer to epoch 2005.0 and plate motion since then can put them decimetres away from current WGS84 positions; for geodetic surveying, deformation monitoring, or any centimetre-grade work, the specific ITRF realisation and epoch matter and should be stated explicitly.

What Is an EPSG Code?

An EPSG code is a short numeric identifier for a coordinate system, maintained in a public registry, for instance 4326 for WGS84 or 23036 for an ED50 UTM zone. Instead of describing a datum and projection in words, you can name the EPSG code and any GIS tool will know exactly what you mean. If you are unsure which code applies to your data, the EPSG Code Finder can help you identify it.

Transformation Parameters Used (Transparency)

This tool performs conversions with Proj4js using the official definitions published in the EPSG registry. We state exactly which parameters are applied:

• ED50 → WGS84 (UTM 6°: EPSG:23029–23038, TM 3°: EPSG:2319–2325, geographic: EPSG:4230): International 1924 ellipsoid and the EPSG transformation defined for the region of the point. In automatic mode: EPSG:1784 for Türkiye (ED50 to WGS 84 (30): dX=-84.1 m, dY=-101.8 m, dZ=-129.7 m, rZ=0.468″, scale 1.05 ppm; accuracy about 2 m), EPSG:1633 for mainland Spain, EPSG:1635 for northwest Spain, EPSG:1631 for the Balearic Islands (about 1.5 m), EPSG:1989 for Portugal (about 1 m) and the western Europe mean EPSG:1133 elsewhere (dX=-87 m, dY=-98 m, dZ=-121 m; about 10 m). The European mean is not applied to points in Türkiye, where it is 8–10 m off.
• You can override the choice: when the source or target is ED50, an "ED50 datum transformation" list appears. The default is "Automatic (by location)"; you can pick another region's transformation manually. The transformation used and its accuracy are shown under the result and included in the PDF report.
• ITRF96 / TUREF (EPSG:5253–5259, 5270–5275): GRS80 ellipsoid; a zero-parameter (identity) transformation to WGS84 is applied. Because TUREF refers to epoch 2005.0, the difference to current WGS84 positions can reach the decimetre level due to plate motion. This is the common approach for everyday GIS and mapping work, not for geodetic surveys.
• Projection constants: Central meridian, scale factor (k=1 for 3° zones) and false easting (500 000 m) are taken from the EPSG definitions.

Note for precise geodetic work: For cadastre, setting-out or deformation surveys requiring centimetre accuracy, use the official transformation surfaces of the Turkish General Directorate of Mapping (HGM) and the TUSAGA-Aktif CORS network. This tool targets metre-level results for planning, checking and everyday GIS use.