[Proj] wgs84 northings and eastings
roger at opq.se
Tue May 24 10:05:03 EST 2011
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
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