Changes between Version 4 and Version 5 of CsMapRfc2

Timestamp:

Jun 16, 2010, 10:44:17 AM (14 years ago)

Author:

Norm Olsen

Comment:

--

CsMapRfc2

@@ -65 +65 @@
 == Implications ==
 
+The proposed changes will not change the numeric results, nor will they change the performance of actual conversions.  The intent of these changes is to remove the dependence upon the WGS84 "pivot datum" model thus enabling more flexibility in defining datum conversions without having to change library code.  The performance of setting up a datum tranformation  (CS_dtcsu) will be negatively impacted, but the actual calulation of a datum shift will remain about the same.
+
 The proposed modifications do not include any changes to existing interfaces, and all existing dictionaries will remain intact.  All foreseen interface changes are additions to the existing API.  What does change, however, is the use of the Datum dictionary.  The transformation information contained in the datum dictionary will now be pretty much ignored; used only in special cases such as producing the "TOWGS84" WKT element.  Thus, existing applications which twiddle the datum dictionary entry and then perform transformations using such changes will be adversely affected; such a technique will no longer work.