[Proj] wgs84 northings and eastings

[Clifford J Mugnier]

ED50 is not a projection.  It is a datum, just like WGS84.
 
Clifford J. Mugnier, C.P., C.M.S.
Chief of Geodesy,
Center for GeoInformatics
Department of Civil Engineering 
Patrick F. Taylor Hall 3223A
LOUISIANA STATE UNIVERSITY 
Baton Rouge, LA  70803
Voice and Facsimile:  (225) 578-8536 [Academic] 
Voice and Facsimile:  (225) 578-4578 [Research] 
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Honorary Life Member of the 
Louisiana Society of Professional Surveyors 
Fellow Emeritus of the ASPRS 
Member of the Americas Petroleum Survey Group


________________________________

From: proj-bounces at lists.maptools.org on behalf of Roger Oberholtzer
Sent: Tue 24-May-11 10:05
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] wgs84 northings and eastings



On Tue, 2011-05-24 at 16:17 +0200, Jean-Claude Repetto wrote:
> Le 24/05/2011 15:24, Roger Oberholtzer a écrit :
> > I have had a request to provide locations (northings and eastings) in
> > wgs84. Up to now, I have always worked with a specific projection
> > somewhere in the world. Such a projection seems rather senseless to me.
> > But there you have it. My question is, given wgs84 lat/longs, how would
> > I request wgs84 northings / eastings from proj. Would this be adequate?
> >
> > +proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 +a=6378137 +b=6378137 +units=m +no_defs
> >
> > Equally worrisome is that I am unsure how to test this as the requester
> > has no sample data. Sigh...
>
> If there is no projection, easting = longitude and northing = latitude.

In fact, this is how I have defined wgs84 up to now. In our system it is
a handy way to get lat/longs that can then be projected somewhere else.
In general use, however, we have always used some local projection
(e.g., ED50 or whatever) to obtain northings /eastings, and were set for
computing distances between points.

The problem is the person requesting this is not an expert in this area.
They are convinced there is a single standard definition for WGS84 as a
projection. As such, they feel they need to specify nothing more than
'wgs84', and northings /eastings will just flow.

I thought maybe they knew something I did not know. Or that there is
indeed a commonly accepted definition of wgs84 as a projection that I
had missed.



Yours sincerely,

Roger Oberholtzer

OPQ Systems / Ramböll RST

Office: Int +46 10-615 60 20
Mobile: Int +46 70-815 1696
roger.oberholtzer at ramboll.se
________________________________________

Ramböll Sverige AB
Krukmakargatan 21
P.O. Box 17009
SE-104 62 Stockholm, Sweden
www.rambollrst.se


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