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

[Jeff McKenna]

Hello Joanne,

Yes, in fact it was me who submitted the custom NRCan EPSG:42304 Lambert 
Conformal Conic projection to the OGP Geodetic Subcommittee. I submitted 
it around January of 2009, and it was accepted around June of 2009. 
They informed me that they added EPSG:3978 and EPSG:3979 accordingly.

Since then I have repeatedly asked NRCan to update their Atlas services 
for these accepted EPSG codes, to no success.  However I have noticed 
that these new EPSG codes are available in most software now, and that 
make me very happy :)

Hopefully this little info help you.

-jeff


-- 
Jeff McKenna
MapServer Consulting and Training Services
http://www.gatewaygeomatics.com/



On 11-06-29 3:42 PM, myOpenLayersUName wrote:
> 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