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Question About Plotting / Converting Locations in a Louisiana Offshore Coordinate System

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#1
Textularia

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Hi,

 

I am working in the Louisiana Offshore Continental Shelf with

some legacy data, including offshore boring logs, for offshore

platforms. The problem is that the location of the platforms are

given in "X COORD" and "Y COORD" coordinates, which is

neither latitude and longitude, state plane, nor any other

coordinate system, with which either I or the GIS experts whom

I know are familiar. I have been told that it was an offshore

coordinate system that was once used for Louisiana Offshore

Continental Shelf, but found out nothing more about it.

 

For example the locations of two offshore platforms in the

Eugene Island Block 273 are given as:

 

Platform            "X COORD"       "Y COORD"

     1                   1,910,712           -91,852

     2                   1,923,081           -85,114

 

The location of offshore platform 1 is also given as

"850 FWL, 750 FSL"

 

Does anyone know what coordinate system that the locations

of the these and similar offshore platforms are given in and

how it can be either plotted or converted to latitude and

longitude?

 

Any help that anyone can provide me would be greatly

appreciated.

 

Yours,

 

Paul

 

Paul V. Heinrich

Baton Rouge, Louisiana

http://lsu.academia.edu/PaulHeinrich



#2
david17tym

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Morning,

Googling " Louisiana Offshore coordinate system" I found the following:

 

§7.  Louisiana Coordinate System defined

A.  For purposes of more precisely defining the Louisiana Coordinate System of 1927, the following definition by the United States Coast and Geodetic Survey, now National Ocean Service/National Geodetic Service, is adopted:

(1)  The "Louisiana Coordinate System of 1927 North Zone" is a Lambert conformal conic projection of the Clarke spheroid of 1866, having standard parallels at north latitudes 31 degrees 10 minutes and 32 degrees 40 minutes, along which parallels the scale shall be exact.  The origin of coordinate is at the intersection of the meridian 92 degrees 30 minutes west of Greenwich and the parallel 30 degrees 40 minutes north latitude.  This origin is given the coordinates: x = 2,000,000' and y = 0', as now defined.

(2)  The "Louisiana Coordinate System of 1927 South Zone" is a Lambert conformal conic projection of the Clarke spheroid of 1866, having standard parallels at north latitudes 29 degrees 18 minutes and 30 degrees 42 minutes, along which parallels the scale shall be exact.  The origin of coordinates is at the intersection of the meridian 91 degrees 20 minutes west of Greenwich and the parallel 28 degrees 40 minutes north latitude.  This origin is given the coordinates: x = 2,000,000' and y= 0', as now defined.

B.  For purposes of more precisely defining the Louisiana Coordinate System of 1983, the following definition by the National Ocean Service/National Geodetic Service is adopted:

(1)  The "Louisiana Coordinate System of 1983 North Zone" is a Lambert conformal conic projection of the North American Datum of 1983, having standard parallels at north latitudes 31 degrees 10 minutes and 32 degrees 40 minutes, along which parallels the scale shall be exact.  The origin of coordinates is at the intersection of the meridian 92 degrees 30 minutes west of Greenwich and the parallel 30 degrees 30 minutes north latitude.  This origin is given the coordinates: x = 1,000,000 meters and y = 0 meters.  

(2)  The "Louisiana Coordinate System of 1983 South Zone" is a Lambert conformal conic projection of the North American Datum of 1983, having standard parallels at north latitudes 29 degrees 18 minutes and 30 degrees 42 minutes along which parallels the scale shall be exact.  The origin of coordinates is at the intersection of the meridian 91 degrees 20 minutes west of Greenwich and the parallel 28 degrees 30 minutes north latitude.  This origin is given the coordinates: x = 1,000,000 meters and y = 0 meters.  

(3)  The "Louisiana Coordinate System of 1983 Offshore Zone" is a Lambert conformal conic projection of the North American Datum 1983, having standard parallels at north latitudes 26 degrees 10 minutes and 27 degrees 50 minutes, along which parallels the scale shall be exact.  The origin of coordinates is at the intersection of the meridian 91 degrees 20 minutes west of Greenwich and the parallel 25 degrees 30 minutes north latitude.  This origin is given the coordinates: x = 1,000,000 meters and y = 0 meters.  

Acts 1985, No. 913, §1.  

 

Any help?

Dave



#3
Melita Kennedy

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Paul,

 

I've heard from my OGP colleagues that even though there is a Louisiana Offshore state plane zone, that it was almost never used. Instead Louisiana South was used. That makes sense based on the fact that the Y values are negative (it's south of the 'valid' area of the zone). Are you sure it's not NAD 1927 Louisiana South (in US survey feet)?

 

The first point ends up at roughly:

 

longitude = -91.613098 

latitude = 28.413655

 

Melita



#4
Textularia

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Dear Dave and Melita,

 

I apologize for my belated reply. However, Baton Rouge, Louisiana, including LSU, was shut down for a couple of days including last Friday, by ice-covered bridges and streets.

 

Thank you for your replies and efforts as both of them provide me with some ideas with which to work.

 

Yours,

 

Paul

 

Paul V. Heinrich

Baton Rouge, Louisiana

http://lsu.academia.edu/PaulHeinrich






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