Question:  How do I convert a NAD27 to NAD83 in projection?

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11-19-2012 05:57 AM
DarrylSanchez
New Contributor II
I recently been sent some shapefiles that are in NAD27 and the projection to NAD83 I am using does not match the output of the bearings and distances from the NAD27 file.  I heard using the transformation NADCON is the best transformer.  Anyone out there know best to convert these shapefiles?
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3 Replies
DarrylSanchez
New Contributor II
Here is some additional information I just received.

"We use NAD27 state plane Montana South in feet" I hope this helps.
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MelitaKennedy
Esri Notable Contributor
The additional information is helpful. You're correct that NADCON, specifically its CONUS (contiguous/continuous US) grid file. In ArcGIS, that's the NAD_1927_To_NAD_1983_NADCON transformation. Because NADCON is a piecewise method (in a way), bearings and distances won't be the same. To get those corrected, you would probably have to have a surveyor re-adjust/resurvey the data.

Melita
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DarrylSanchez
New Contributor II
This data was collected by GPS and the points sent to me were in NAD27 Stateplane Montana South.  What I have discovered when the connect the points to create lines they can determine the bearings and distances, however the bearings do not match.  What I am also finding out is that they create the transformation after they lines are generated and that data is sent to me.  What I have now done to correct these errors is to have them send me the points in NAD27 and I will do the re-projection to NAD83 stateplane FIPS feet, but what is needed is the right transformation.  From there I can create the lines and then open up the traverse tool and click editing and have the transverse data captured from by loading travers from sketch.  That way I can send him back this data through a save traverse file and he can send me back the survey.  Fun huh!

3D darryl

P.S. Read the paper I submitted to the 2012 International Conrference on the topic of 3D titled "To 3D or not To 3D" how Jack has convinced us that the world is flat again.
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