Horizontal Coordinate software-NAD27 to NAD83

What software do you use to convert 27 to 83? Geographic calculator or other?

CORPSCON6

http://crunch.tec.army.mil/software/corpscon/corpscon.html

This functionality is also built-in to software like Civil 3D and Carlson Civil.

Howdy,

Before using any software to perform this computation, I'd certainly want to know how it is performed.  The official federal government standard is NADCON. This NGS-developed software package consists of an interpolation tool linked to a file of  gridded coordinate differences based on shifts at points common two systems (NAD 27 and NAD 83 as well as NAD 83 and subsequent upgrades to NAD 83).  Be sure to know what version of NAD 83 coordinates you have. See the Professional Surveyor article linked to the tool and the tool documentation on the NGS web site. 

CORPSCON is an interface developed to make it easier to use the NGS programs: NADCON, VERTCON, SPCS83 and GEOID (up to GEOID03).  They use NGS algorithms and grid files.  I note that the most recent version has not been updated to include GEOID09.  

How other programs perform this computation must be determined.  It is possible to use the Molodensky method (based on the differences between reference ellipsoids parameters and origins) to derive an NAD 83 coordinate from NAD 27.  The answer will almost always differ from that using NADCON.       

Given that NADCON is the federal standard and that it includes data derived from points common to both systems, I use it.  I would hope the method used in the various packages would be clearly stated.  I believe most use NADCON and its grid files.  

Cheers,

DMM

Corpscon will use GEOID09, I posted a link to instructions on how to do it. Here is the link again (file name changed from before)

http://www.terrasurv.com/Corpscon-Geoid09.pdf