This are the neccessary steps to get 
full map datum support within GRASS:

- change coorcnv library calls to use $GISBASE/etc/datum.table
done.

- change coorcnv library to use ellipsoids in 
$GISBASE/etc/ellipse.table
done.

- add datum support functions to coorcnv library:
datum shift parameters:
+ CC_get_datum_by_name
+ CC_get_datum_by_nbr
x CC_datum_name
x CC_datum_description
+ CC_datum_ellipsoid
x CC_datum_shift -> CC_get_datum_parameters
+ CC_get_datum_parameters ( or CC_get_datum_parameters3?) 
  CC_get_datum_parameters7

spheroid/ellipsoid parameters:
(only wrappers for libgis calls!)
* CC_get_spheroid
* CC_spheroid_name
+ CC_get_spheroid_by_name
+ CC_get_spheroid_by_nbr
(reworked and new gislib calls)
+ G_ellipsoid_name
+ G_get_spheroid_by_name (for f parameter)
+ G_ellipsoid_name
+ G_ellipsoid_description
* G_get_ellipsoid_by_name
* G_get_ellipsoid_parameters

datum shift routines:
+ CC_datum_shift_Molodensky
+ CC_datum_to_datum_shift_M
+ CC_datum_shift_CC
+ CC_datum_to_datum_shift_CC
+ CC_datum_shift_BursaWolf
+ CC_datum_to_datum_shift_BW

others:
+ CC_geo2lld
+ CC_lld2geo

symbols:
? not known
x changable, because not used in any module
* existing, not changable
+ new
  not yet implemented
mostly done, needs testing. 

- change m.datum.shift to new library calls
done, needs testing. 

- add functions for low-level datum support to gislib 
(in analogy to the ellipsoid and projection functions):
add metadata (datum name and parameters) to PROJ_INFO 
to every PERMAMENT mapset of locations. 
This is done via g.setproj i assume (please correct me
if i am wrong!)

proposed format: 
datum:  acronym
ellips: acronym -> already there
dx: -> shifting parameter dx relative to wgs84
dy: -> dy
dz: -> dz
a:  -> already in PROJ_INFO
e2: -> already in PROJ_INFO
f:  -> from ellipse.table

- add a function to read the datum parameters for the 
actual location (parallel to G_database_projection_name 
and G_get_ellipsoid_parameters)
+ G_database_datum_name()
+ G_get_datum_parameters(a, e2, f, dx, dy, dz)
+ G_get_datum_parameters7(a, e2, f, dx, dy, dz, rx, ry, rz, m)

- add G_ask_datum_name for interactive use in modules
+ G_ask_datum_name()
done.

- change all modules that create new locations to
ask the user for a map datum and add to PROJ_INFO file.
This is done via g.setproj.

- change all modules that do projection or data-import 
to use datum conversion:
v.proj
r.proj
s.proj
r.in.*
v.in.*
etc.

Please note that i am only involved with the first steps of 
changing the library to support map datums. The changes in 
the modules must be done by other GRASS developers or
the module maintainers.

Andreas Lange, 05/2000,
andreas.lange@rhein-main.de