Datum Shift Between ED50 and WGS84
The longitude and latitude lines on the two datums are the same in the Archangel region of north-west Russia. As one moves westwards across Europe, the longitude lines on ED50 gradually become further west than their WGS84 equivalents, and are around 100 metres west in Spain and Portugal. Moving southwards, the latitude lines on ED50 gradually become further south than the WGS84 lines, and are around 100 m south in the Mediterranean Sea. (NB. If the lines are further west, the longitude value of any given point becomes more easterly. Similarly, if the lines are south, the values become northerly.)
(This doesn't mean Europe has expanded. The International Ellipsoid is larger than the GRS80/WGS84, so a given north-south distance will cover more latitude on the new ellipsoid, and a given east-west distance will cover more longitude.)
The datum shift for the Universal Transverse Mercator grid is different. The eastings vary between 0 m in Eastern Europe and 100 m in the far west of the continent, roughly similar to the longitude shift, but the northings are about 200 m different across Europe, with the ED50 UTM northing lines south of the WGS84 UTM northing lines, as UTM northings are measured from the Equator, and the theoretical ED50 Equator is about 200 m south of the WGS84 one.
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