A question about projection when creating a new shapefile

Question

My data frame projection is WGS 84 (taken from the several ESRI basemaps loaded in the data frame). I brought in some GPS points which were taken in NAD27.  They were projected on the fly to match the data frame projection. I need to create a polygon based on these GPS points. I'll eventually need the polygon information to be in NAD27. My question is: because I'm creating a shapefile based on the GPS points in WGS84, do I need to set the new shapefile projection to WGS84? Or can I set the projection to NAD27, then, as I create the polygons, they will be shown correctly in the data frame, and still truly be NAD27?

Thanks!

NeilAyres · Answer

As a GIS person I always advise clients when I see a business (mines, utilities, many others), having their main db in a coordinate system based on a classical datum, to bite the bullet, and transform the data now. Otherwise the problems just keep mounting up. Every new data capture project (aerial imagery, lidar, ground GPS etc etc), has to be transformed by some means on to the old datum. Question is, how is that transformation achieved. This part of the workflow is rarely, if ever, documented properly (usually because most people don't understand the implications). So you end up with a db which contains a whole bunch of historical stuff and more modern layers which never, ever, quite line up. And it is impossible to ever get everything sorted out.

JoeBorgione · Answer

...Archaeologists like old stuff...

So it seems!

WilliamsonElizabeth · Answer

lol! Well, the repository for all of the archaeological site data in Georgia requires site UTMs to be NAD27. It's what's been used since the Georgia Archaeological Site File was established way back when. I guess they feel it's too late to change. Also, archaeologists like old stuff