Layers don't line up after converting from NAD27 to NAD83

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03-05-2012 08:12 AM
JamesRichards
New Contributor
I have been exporting my GPS (.cor) files to shapefiles for use in ArcMap using Trimble Pathfinder office in the  NAD27 system. All my shapefiles which eventually end up in feature classes have been using NAD27.  In an effort to convert to NAD83, I have been exporting my new GPS files to shapefiles in the NAD83 system. After I convert an old NAD27 feature class to NAD83 and try to overlay a new shapefile (or feature class from that shapefile) that has been exported directly to an NAD83 shapefile, there is an offset of a few meters. So basically, everything that is originally NAD27 and now NAD83 has a few meter offset when used with NAD83 layers. As of now, the only way I have found to correct this offset is to start an editing session and nudge the converted NAD27 to NAD83 layer until it lines up with newly acquired shapefiles and feature classes in the NAD83 system.

Is this small offset common? Any help would be greatly appreciated.

Thanks
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MelitaKennedy
Esri Notable Contributor
My guess is that different transformations are being used. That could cause small offsets like that. Particularly in Trimble Pathfinder Office, I don't know how to check what is being used.

Melita
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