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I'm trying to plot some X,Y coordinates which should be located on Jersey (the British dependency, not the state).

The metadata that came with the points is as follows:

Coordinate System: Transverse_Mercator
False_Easting: 500000.000000
False_Northing: 0.000000
Central_Meridian: -3.000000
Scale_Factor: 0.999600
Latitude_Of_Origin: 0.000000
Datum: D_European_1950
Prime Meridian: 0

An example coordinate is: 40844, 68194

However, when I try to put this into QGIS or ArcGIS, I end up with points near latlng 0,0. What am I doing wrong? How do I reference these points correctly, so I can plot them over a basemap?

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up vote 8 down vote accepted

Whoever thought this was ED50 UTM Zone 30 North was incorrect. The values instead match ETRS 1989 / Jersey TM, EPSG: 3109.

Esri's version:

WKID: 3109 Authority: EPSG

Projection: Transverse_Mercator
False_Easting: 40000.0
False_Northing: 70000.0
Central_Meridian: -2.135
Scale_Factor: 0.9999999
Latitude_Of_Origin: 49.225
Linear Unit: Meter (1.0)

Edit: Upon reflection, I thought I would expand this answer. How did I know it wasn't UTM? In the northern hemisphere, the Y / northing origin is at the equator. Y values gain about 1 million meters per 10 degrees, so mid-latitudes are 4-5 million.

This isn't easily replicated, but drawing on my experience and memory, I thought there was a projected coordinate reference system for the Isle of Jersey. To check it, I searched for Jersey in ArcMap's data frame properties, Coordinate System tab. Otherwise, I could have checked the EPSG online registry. Another place to check is Spatial Reference, but just know that the latter website is not curated (checked) in any way (there's a lot of duplicates, etc.).

Disclosure: I'm on the subcommittee that maintains the EPSG registry. (This doesn't mean that there are no errors in the EPSG registry, but we try our best to avoid them!)

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