[Proj] datum matters

Noel Zinn ndzinn at comcast.net
Sun Mar 29 18:04:09 EST 2009


Good!  And thanks for your clarification, with which I agree.  I am betwixt
and between on this issue.  Cartography is a marvelous entertainment in the
abstract that needn't be / shouldn't be encumbered with a datum.  However,
once culture is presented on the map (other than a cartoon coastline or some
such for reference), then the geodetic datum is critical.  In this era of
computers and GIS, the issue of small scale versus large scale is
irrelevant.  Before culture ever gets to a paper map where scale is
relevant, it lives forever in a database and can be re-presented at any
scale one might (mistakenly) desire.  That's not good.  So, I guess I agree
with you for cartoons, but not for real data.  




From: proj-bounces at lists.maptools.org
[mailto:proj-bounces at lists.maptools.org] On Behalf Of strebe
Sent: Sunday, March 29, 2009 5:31 PM
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] datum matters


On Mar 29, 2009, at 1:45:42 PM, "Noel Zinn" <ndzinn at comcast.net> wrote:

Fictitious datum?  That's offensive, daan.  When the datum is ignored,
cartography is an entertainment merely purporting to represent the real
world.  That's fine, but (the) datum is hardly fictitious.  -Noel 


Noel: I did not call the datum fictitious in general. Please read more
carefully so that people do not get attributed with and then taken to task
for words and ideas they do not espouse.


If no datum is attached to the coordinates, and if the projection/coordinate
conversion software requires a datum because it has conflated projection and
coordinate transformation, then the user would be forced to declare some
fictitious datum in order to satisfy the ideological requirements of the
software. That is what I referred to as a "fictitious datum". If that is
"offensive", then feel free to elaborate, though I am very much at the point
of bowing out of the conversation. (I will not, however, take my marbles and
go home.)



- daan Strebe

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