Vedr: [OSRS-PROJ] NTv1 (Canadian) Grid Shifts, and proj_def.dat

Gerald I. Evenden vze2hc4d at verizon.net
Fri Apr 6 10:49:22 EDT 2001


The major point of building in the proj_def.dat system was to make
proj.4 easily responsive to local needs.  Any and all users should
take benefit of this feature and change the "default" ellipsoid to
whatever suits their local needs.

The use of Clarke 66 only reflects what was the common ellipsoid
in use at the time and location of development.

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PS. Please note that I have change ISP provider and note the
change of my email address to vze86wal at verizon.net

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Thomas Knudsen wrote:

> > Second, I would like to change proj_def.dat to provide a default
> ellipsoid
> > of WGS84 (really would make it +datum=WGS84).  The assumption is that in
> > this day and age WGS84 is a better default than clrk66 (normally NAD27).
>
> Wouldn't it be better to select GRS80 as the default ellipsoid? (obviously,
> the
> difference would be minor, but GRS80 is the one actually recommended by
> the International Union of Geodesy and Geophysics (IUGG)
>
> --
> Thomas Knudsen, Research Geophysicist, Ph.D. |
> National Survey and Cadastre - Denmark       | thk at kms.dk   tk at gfy.ku.dk
> Geodetic Department, Rentemestervej 8        | phone:    +45 35 87 52 64
> DK-2400 Copenhagen NV, Denmark               | phaks:    +45 35 87 50 52
>
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