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I have a dataset that I have pulled from a MaxSea 3d database.

I am trying to figure out what projection is used, so I can transform and use the data. I have tried following this guide http://support.esri.com/en/knowledgebase/techarticles/detail/24893, for a small sample of data (300k points). Firstly, the fields are named lat and lon, indicating a Geographic Coordinate System (datum), but the data given looks more like it is in a Projected Coordinate System, becuase the numbers are in 8-9 digits range.

The data on file is collected around the Faroe Islands, and if the data is in Geographic Coordinates, it should be in or around 62°N and 7°W ± a few degrees, so I can conclude that the data is not in any format where the leading digits are degrees. (not decimal degrees or DDMMSS.ss, as suggested here).

That leaves me with either a proprietary, unknown projection (possible!), or it is in a Projected Coordinate system. I keep on following the Esri guide, to figure out what Projection is used, and this is where I need help, because the Esri guides only covers the U.S.

If the data is in the United States and shows an extent in which the coordinates to the left of the decimal are 6, 7 or 8 digits, the data is probably projected to the State Plane or UTM coordinate systems.

screenshot

Here I see that there are 9 digits (!) left to the decimal point, and when I try to add some reference data, I find that my data is outside the extent of the earth.

What would you try, I you were asked to figure out the projection of the data?

Here is a sample of the data (50k points). The fields are: id, level, lat, lon, weightdepth_cmap, valuedepth_cmap, weightdepth, valuedepth. The fields of interest are lat, lon.

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1 Answer 1

The best way to get the projection would be to ask the provider.

Looking a bit at the data, the first column looks (Northing) like Google Map coordinates (EPSG:3857), but in centimetres.

The second one should be negative for the Faroers, but adding a false Easting at 180°West (which is around 20.000.000 metres from 0°), could lead you to your area, if your data is in centimetres.

Maybe they have taken another value for false Easting, or other ellipsoid parametres for projection.

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I am currently in contact with the provider of the data, but I have not received an answer yet. I will try adding the data as centimeters, and post the results here. Thanks! –  Ragnar123 Jun 15 '13 at 15:40
    
It looks like another value is used for false Easting. I will keep you posted on what I find. –  Ragnar123 Jun 15 '13 at 22:12

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