Newsgroups: info.grass.user
Path: zorro.cecer.army.mil!shapiro
From: shapiro@zorro.cecer.army.mil (Michael Shapiro)
Subject: Re: shifting DLG data
Message-ID: <C3I3oH.8Mp@news.cecer.army.mil>
Sender: news@news.cecer.army.mil (Net.Noise owner)
Organization: US Army Corps of Engineers Construction Engineering Research Labs
References: <01GUTU9KOCEO8ZDVO3@CWU.BITNET>
Date: Sun, 7 Mar 1993 04:12:17 GMT
Lines: 21
In <01GUTU9KOCEO8ZDVO3@CWU.BITNET> GEOL1@cwu.bitnet writes:
Simply using the "correct spheroid" won't do it if the conversion
in from NAD27 to NAD83. Apart from using a different spheroid, the
datum is different. NAD83 is earth centered, while NAD27 is not.
The 175 meter error is of the right magnitude to be caused
by improper matching of UTM "spheriods". The DLG data was
likely produced referenced to the "clark66" (NAD27) spheroid,
and your GPS may be using a more modern spheroid.
You could use m.ll2u and m.u2ll to convert your GPS
control points to the different datum.
Jim Hinthorne
GIS Lab
GIS Lab
--
Michael Shapiro U.S. Army CERL
Environmental Division