lets see.. First you're doing something wrong when doing your coordinate transformation in your database. If you have an original Xold,Yold in Nad27 and a new coordinates Xnew Ynew in Wgs84, the actual values between the column I think should be : Xold~Xnew (to less than a meter) Yold~Ynew-215 So I'm not sure what's happening with your data there... MAybe you can send me the original ply if you want...
----- Original Message ----- From: "David Humphrey" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Tuesday, June 25, 2002 4:59 PM Subject: RE: [geonet]: Mixing data from different projections on a map > Hi, Fred. Funny that we're carrying on interoffice communication on a > public listserver, but I'll reply here for completeness of the thread. > > I think one of the experiements I've done over the past couple of days > includes your procedure. > > 1. I saved the polygons from the NAD27 map into a .ply file, converted it > to a .xyz file of lines, imported it into a new database, and attached > appropriate NAD27 projection information to that (X,Y) pair. > 2. I did a coordinate transformation of this (X,Y) pair to the WGS-version > parameters producing a pair of channels named XW84 and YW84. > 3. When I post either of these coordinate sets as lines, they post directly > on top of each other even though the actual numbers in the channels are > different by ~3 meters in the X coordinates and ~21 meters in the Y > coordinates. > > From this experiment, I infer that Oasis is handling things consistently > internally. > > However, and here's the rub, when I post the original .ply file that I saved > from the NAD27 map, the polygons appear ~215 meters north of those lines I > posted from the database (how did we ever live without the Ruler feature?). > Recall that this file has NAD27 projection information in header records > that begin with /#. > > To see if these header records have some effect, I removed them from the > .ply file and posted again. The polygons post in yet a 3rd position - very > near those from the lines database. > > Any thoughts? > > Regards, > DLH > _______________________________________________________ > More mailing list info http://www.geosoft.com/support/listserv/index.html _______________________________________________________ More mailing list info http://www.geosoft.com/support/listserv/index.html
