[mapserver-users] EPSG:42304 -> EPSG:3978? or 3979?

[myOpenLayersUName]

Hello all,
I know this isn't really a MapServer question, but I know that some of the
people involved in this stuff read this forum and don't know where else to
post it. 

I'm trying to understand if the old, unofficial, NRCan EPSG:42304 code
(often used in Canadian MapServer installations) translates to the new
official EPSG:3978 or EPSG:3979 code. But, I can't figure out the answer and
am hoping that someone who reads this can straighten me out. I know little
about projections at this level and apologize if I'm using the wrong
terminology or am passing along mis-information in asking for clarification.

There was an custom EPSG code that many, in Canada, used in MapServer
installations, EPSG:42304. From what I understood, it was a projection
defined by Natural Resources Canada and others adopted it as a kind of
unofficial "standard". The only definition of that projection I've been able
to find, in terms of how to define it in a PROJ4 file (which is why I'm
looking for it) is at: http://spatialreference.org/ref/sr-org/6754/, where
its parameters are specified as:

+proj=lcc +lat_1=49 +lat_2=77 +lat_0=49 +lon_0=-95 +x_0=0 +y_0=0
+ellps=GRS80 +datum=NAD83 +units=m +no_defs

I was led to believe this projection was submitted for inclusion as an
official EPSG code and that it had been approved. Now, there's two official
EPSG codes that I've found that seem to be similar. They are EPSG:3978 and
EPSG:3979. Using the EPSG Registry's (http://www.epsg-registry.org/)
"retrieve by code" tool, I've looked at the definitions of 3978 and 3979 and
can find the only difference between the two to be their Geodetic Datum (one
being Canada and one being North America) which ultimately only seems to be
different with respect to their "Area of Use".

When I look at the PROJ.4 site's EPSG list
(http://svn.osgeo.org/metacrs/proj/trunk/proj/nad/epsg), the entries for the
two are the exact same, which suggests my interpretation of the "Area of
Use" being the only difference might be correct.

# NAD83 / Canada Atlas Lambert
<3978> +proj=lcc +lat_1=49 +lat_2=77 +lat_0=49 +lon_0=-95 +x_0=0 +y_0=0
+ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs  <>
# NAD83(CSRS) / Canada Atlas Lambert
<3979> +proj=lcc +lat_1=49 +lat_2=77 +lat_0=49 +lon_0=-95 +x_0=0 +y_0=0
+ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs  <>


Unfortunately, neither of these parameter lists are exactly the same as the
42304 definition from above (these have "+towgs84=0,0,.." and the 42304 one
has "+datum=NAD83"...for all I know, those two parameters are defining the
same thing).


So, my question is: Are either of these official EPSG codes actually the
same as that unofficial 42304 code?

Cheers,
jtm

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