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Newsgroups: info.grass.user
Path: zorro.cecer.army.mil!shapiro
From: shapiro at zorro.cecer.army.mil (Michael Shapiro)
Subject: Re: shifting DLG data
Message-ID: <C3I3oH.8Mp at news.cecer.army.mil>
Sender: news at news.cecer.army.mil (Net.Noise owner)
Organization: US Army Corps of Engineers Construction Engineering Research Labs
References: <01GUTU9KOCEO8ZDVO3 at CWU.BITNET>
Date: Sun, 7 Mar 1993 04:12:17 GMT
Lines: 21

In <01GUTU9KOCEO8ZDVO3 at CWU.BITNET> GEOL1 at 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