I had similar issues with conversions until I learnt enough about
co-ordinate systems to understand why I needed to specify co-ordinate
systems for layers before I started entering data.
I suspect you will find that if you were using the generic Longitude -
Latitude "projection" then as it does not have a specified "projection"
(hopefully using the word to mean the same thing as MI do in the program) or
ellipsoid, it will align itself to the bottommost layer where a "projection"
has been specified.
Thus, if you have a WGS84 layer below it, it may well have picked that
"projection" up.
I would also hazard a guess that in the absence of any specified in a layer,
the generic Longitude - Latitude "projection" defaults to the GRS80
ellipsoid (MI ellipsoid #0) or perhaps the WGS72 ellipsoid (ellipsoid #1)
either of which appear to be sufficiently close to WGS84 for it to be
unlikely that you would spot a difference in the resultant co-ordinates. I
repeat that I am only guessing regarding a default value...
Either way, if the "projection" was not specified, there is little surprise
if the co-ordinates did not shift.
It would pay to check the co-ordinate system the original data was derived
from to be sure that the non-shift has left you with valid co-ordinates.
Regards
Russ MIncher
----- Original Message -----
From: Humphrey, Ben <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, November 02, 1999 10:28 AM
Subject: MI lat/long to WGS84 - shouldn't there be a difference!?
> So there I was saving a table from lat/long into lat/long WGS84 and I
> realized upon completion that there was absolutely no difference between
the
> coordinates before and after the projection.
>
> So my questions are: Is there a difference? Shouldn't the coordinates
> shift a little between projections? I've never dealt much with changing
> projections so I am at a bit of a loss here.
>
> Thanks to anybody who can provide some enlightening suggestions.
>
> Ben Humphrey
> Mapping Specialist
> VoiceStream Wireless
> 425-653-4605
>
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