About geographic transformations and how to choose the right one

re: About geographic transformations and how to choose the right one

mattfindley — Fri, 08 May 2009 15:56:15 GMT

Thanks. The graphics distinguishing geocentric and geodetic concepts was helpful. Any ideas on how to choose between lists of other transformations like NAD83 <-> WGS84 that have several varieties? For example, the differences between the following transformation functions aren't real clear (at least between 2 and 3):

NAD_1983_HARN_To_WGS_1984

NAD_1983_HARN_To_WGS_1984_2

NAD_1983_HARN_To_WGS_1984_3

Almost scared to ask, but what's the significance of all the dx, dy, dz parameters that appear at the bottom of the dialog box when loading a transformation function?

re: About geographic transformations and how to choose the right one

maphew — Fri, 05 Jun 2009 19:38:09 GMT

this article needs just a few more pictures, these ones here for example: http://yukongis.ca/bin/view/Main/WebForum#nabble-p12172118 Since they came from ESRI literature to begin with, it is only natural they should be here too!

Since posting the above thread, I've also been asked several times for similar images for transformations for other parts of the globe.

re: About geographic transformations and how to choose the right one

Helenak — Thu, 19 Nov 2009 10:51:18 GMT

Dear Dr. Buckley,

Your explanation is much better than my GIS teacher.

Thank you very much.

Recently, I have a problem transferring GCS 1984 (unit: degree) to Behrmann (unit: km).

The projection was all right, but the unit was not.

Do you have any advice ?

Thank you in advance.

Elaine