[geonet]: Projections

[Aaron Balasch]

Something I've been wondering about for a long time but never took the time to figure out the intricacies of it. I just learned how to do what I needed and never minded the rest. I finally took the better part of this morning reading the book about projections. I don't have a solution, but it seems to me that there must be a way to cut down the amount of information(i.e. about 50 different ellipsoids, about 50 different local transformations, etc). For instance, is Bessel 1841 used anywhere, is Airy 1830 neccessary - doesn't Airy modified 1849 replace it, etc.   After reading through the book and help files, I still have a couple questions. When I but a topographic map of Canada(of say B.C.) it says it uses the NAD27 ellipsoid. It doeasn't say what local transformation it uses? One might assume that it's [NAD27]Canada(AB/BC) but assumptions can be dangerous. I also went through all the mapproj.csv, ldatum.csv, etc. files. I found where the ldatum.csv file calls the datum for say [Nad 27]Canada(Ont.&Man.) but couldn't find the call to the appropriate datum for [Nad27]Canada(BC./AB). Did I just not look hard enough?       Aaron Balasch Sky Hunter Technologies Inc. Suite 101, 1725 10th Avenue S.W. Calgary, Alberta T3C 0K1 Phone: (403)228-2175 Fax: (403)244-7955 email: [EMAIL PROTECTED]