it should work but to test create a database and copy/paste your polygone coordinates in it. Then do a "new projected corrdinates" operation using : 1 Nad 27 etc... as your original coordinated 2 WGS84 etc as your new coordinates copy/past the result in new .ply files (simple ascii file with one column of x, one of y) and plot those new files in your wgs84 map. They should match yout original polygons if Oasis as handled the datum change dirrectly.
----- Original Message ----- From: "David Humphrey" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Tuesday, June 25, 2002 3:16 PM Subject: [geonet]: Mixing data from different projections on a map > The more I work with geodesy, I realize how much more I don't know about it. > A project I am currently working on is a case in point. > > We have a Geosoft map from another source that was constructed with the > following parameters: > > datum: NAD27 > ellipsoid: Clarke 1866 > Projection: UTM Zone 16N > local datum: [NAD27] MEAN CONUS > > This map contains some polygons that I want to put on a second map. This > second map was constructed with the following parameters: > > datum: WGS 84 > ellipsoid: WGS 84 > Projection UTM Zone 16N > local datum: [WGS 84] World > > What is the best process that I can use so that I am sure that these > polygons are posted in the right place on this second map? One thing that I > have done is: > > 1. In the first map, use Mapping->Get Polygons from a Group. I find that > this creates a polygon file with some header records containing projection > information. > 2. In the second map, use Mapping->Draw from Polygon File. Indeed, the > polygons appear on the map. > > Are they in the right position? I have reason to believe that Oasis montaj > uses the header information to do coordinate transformations on-the-fly to > insure that the points are properly placed, but want to check with some > authorities in the Geosoft community to be sure. Are there simple > experiments one can run that will demonstrate this? > > Regards, > David Humphrey > Director, Technical Services > Bell Geospace, Inc > > _______________________________________________________ > More mailing list info http://www.geosoft.com/support/listserv/index.html _______________________________________________________ More mailing list info http://www.geosoft.com/support/listserv/index.html
