Question About Transformation Methods

[JasonFultz]

I have a few questions regarding datum transformations that I haven't been able to find a solid answer to yet and I'm hoping someone can shed some light on these topics.

1.  I occasionally find that when I incorporate data with differing datums into GIS the transformation method that fits the best with the aerials or base data is when I leave the transformation method set to "None".   Is this incorrect to leave the method as None?  Should all data with differing datums be assigned one of the transformation methods?

2.  What is the best method of transforming from NAD83 to NAD27?  I have read up on this but I seem to only find methods of transforming from NAD27 TO NAD83.  I know ArcGIS will make suggestions and rank the appropriate transformation methods based on your data, but I only see methods for transforming from NAD27 TO NAD83.  The data lies in the continental US.  Any suggestions?

Any insight to these questions would be much appreciated.

Thanks!

Jason

[DanPatterson_Retired]

In your system path

C:\Program Files (x86)\ArcGIS\Desktop10.2\Documentation\geographic_transformation.pdf

about page 25 ... NOW the transformations work in BOTH directions as you will glean from all the transformations there, the always go from oldest to newest since the reverse has to be true

[JasonFultz]

Dan, Thank you for pointing me towards the document.  It makes complete sense hearing that the transformations work in both directions.  Thanks for the insight! 

Jason