AW: [Mapserver-users] RE: latitude and longitude

Mon Mar 17 09:29:09 EST 2003

One significant source of confusion in the USA in this area is in the 
terminology.  When one is discussing plain surveying, one uses Y,X by 
convention, but there is little confusion.  We actually use the terms 
'Northing' and 'Easting' to discuss offsets from a reference point.  The 
main confusion then is in terms of units of measure: feet vs meters.  Of 
course, once one gets past the initial question of N v W and Lat v Lon, 
one comes back to the myriad projection possibilities.  If I'm using UTM 
Zone 15 North, I can easily have a set of coordinates that, if 
unreferenced, look a lot like UTM-2-N, but are half a world away.

And this discussion completely ignores the possible confusion arising 
from an Earth Reference Frame discussion of 3-axis cartesion 
coordinates, and similarly ignores datum and ellipsoid considerations.

So: What's the answer?  *Metadata*.  If Metadata is maintained and 
transmitted as an essential element of all spatial records, we have a 
chance of diminishing the confusion.

Gerry

Arnulf Christl wrote:
> Hi,
> this contribution is just (hopefully helpful) background noise about
> coordinate communication:
> 
> In Germany we often have a problem of mixing up x and y coordinates between
> the-common-GIS-hacker and survey engineers. Survey engineers use the writing
> notation (y, x) to code coordinates which tends to be rather confusion for
> us "normal" GIS hackers.
> Therefore if we (dare to) talk to survey engineers we usually say
> "Rechtswert", which could be translated into "right value". What we mean is
> "easting", "x" or "Längendgrad" (longitude).
> We say "Hochwert" which translates into "up-value" and what we mean is
> "northing" or "y" or "Breitengrad" (latitude).
> Another problem is that (x, y) coordinates are commonly mixed up by german
> talking when a "Latitude" or "Longitude" is requested. We are not used to
> these terms in day to day work.
> It is a very common potential error for any european reading english
> documentation and trying to implement demo data or getting anything to run.
> 
> At least most of us around here use "north" as the top for our maps, no
> misunderstanding there...
> 
> Cheers,
> Arnulf
> 
> -----Ursprüngliche Nachricht-----
> Von: mapserver-users-admin at lists.gis.umn.edu
> [mailto:mapserver-users-admin at lists.gis.umn.edu]Im Auftrag von Ed
> McNierney
> Gesendet: Freitag, 14. März 2003 16:34
> An: havard.tveite at ikf.nlh.no; mapserver-users at lists.gis.umn.edu
> Betreff: RE: [Mapserver-users] RE: latitude and longitude
> 
> 
> Håvard -
> 
> What exactly do you mean?  Do Norwegians like maps where East is up at the
> top?  Or are you talking about projected coordinate systems, rather than
> latitude and longitude?
> 
> 	- Ed
> 
> Ed McNierney
> President and Chief Mapmaker
> TopoZone.com / Maps a la carte, Inc.
> 73 Princeton Street, Suite 305
> North Chelmsford, MA  01863
> ed at topozone.com
> (978) 251-4242
> 
> -----Original Message-----
> From: Havard Tveite [mailto:havard.tveite at ikf.nlh.no]
> Sent: Friday, March 14, 2003 10:26 AM
> To: mapserver-users at lists.gis.umn.edu
> Subject: Re: [Mapserver-users] RE: latitude and longitude
> 
> 
> In Europe (in Norway, anyway) the tradition is to use x for
> north and y for east.
> I don't like it, but it is difficult to convince the surveying
> and geodesy people to change to the more intuitive(?) x for
> east and y for north.
> 
> Ed McNierney wrote:
> 
>>If you are working with a map in a "geographic" projection (where you
> 
> assume latitude and longitude make a rectangular grid) then the longitude
> (east-west) is usually the X coordinate, and latitude is usually the Y
> coordinate.  There's no reason you couldn't turn the Earth so the equator
> was a vertical line up the middle of your map, but people just don't seem to
> do it that way.
> 
>>	- Ed
>>
>>-----Original Message-----
>>From: ryanne cruz [mailto:ryanne.cruz at up.edu.ph]
>>Sent: Thursday, March 13, 2003 10:36 AM
>>To: mapserver-users at lists.gis.umn.edu
>>Subject: [Mapserver-users] RE: latitude and longitude
> 
> ...
> 
>>im sorry if this had been asked before and i have read someone post that
> 
> when
> 
>>you query for x(geom) you are referring to the longitude and y(geom) with
> 
> the
> 
>>latitude. is this correct? because i am getting very confused!
>>
>>thanks for all the help. we will soon be uploading our site and i hope
> 
> you'll
> 
>>have the time to see it. i'll post next time our website.
>>
>>ryanne
> 
> 
> --
> Håvard Tveite                       Phone:  +47 64948857
> Department of Mapping Sciences      Fax:    +47 64948856
> Agricultural University of Norway  http://www.nlh.no/ikf
> Hogskoleveien 14, POBox 5034, N-1432 Ås, NORWAY
> 
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-- 
Gerry Creager -- gerry.creager at tamu.edu
Network Engineering -- AATLT, Texas A&M University	
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.847.8578
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