I have used two different online coordinate converters to convert Lambert coordinates 386.1/1185.0 to Lat/Lon and receive an answer 47.42715241/-5.62147696. This reference is 426 kms on a bearing of 242 deg from the known position of the place to which the Lambert reference is given.

  • Is either online converter available to the public? I'd like to run some sample points on them. – mkennedy Apr 11 '16 at 17:25

I think you may have used the wrong dimensions. Projected Coordinate systems usually take meters as units, and your point should be in the North of France (Lambert Nord, Lambert 1 has an additional shift of 1000000 Northing).

If you enter coordinates in kilometers, they will end up at the origin of the projection, which is off the Atlantic Coast:

enter image description here

So try 386100 / 1185000 and you should get the right degree coordinates.

| improve this answer | |

I believe there is a confusion between EPSG:27561 and EPSG:27571. Here are the differing parameters between the two:

NTF (Paris) / Lambert Nord France
False Northing: 200000 m

NTF (Paris) / Lambert zone I
False Northing: 1200000 m

That would explain the differing latitude values. I think the online converters may be returning longitude values relative to the Greenwich prime meridian rather than Paris one (Thus NTF or WGS 1984 not NTF (Paris)).

I haven't check it, but there could be a grads versus degrees issue as well.

In the Esri projection engine, if I use 27571, the results are

54.808375149 -3.2706144771 (NTF (Paris), grads)

If I use 27561,

64.7429894875 -4.0008561734 (NTF (Paris), grads)

Ah, even with changing the values from grads to degrees, I'm still not matching your results, so without checking the online converters, I don't know if this completely answers your question.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.