> The proj library is updated in everything but the make process,
which I
> think is in Glynn's capable hands.
It should be done, in that the .lla files are being compiled and
stored in $GISBASE/etc/nad.A couple of issues:
1. Should the ntv1_can.dat file be copied to $GISBASE/etc/nad also?
Yes. That file is necessary for conversions in Newfoundland and in most
of Canada north of 50 degrees N; it is the preferred data for any
location in Canada. The modules aren't currently using that grid, but
the proj library can use it and I expect the modules will be updated to
use it in the near future.
2. What's the situation with the two-letter files (FL.lla etc)?
According to nad/README (in proj-4.4.5), these are NAD83->NAD83,
whereas the others (e.g. conus.lla) are NAD27->NAD83. Are they meant
to be applied as a "correction" after NAD27->NAD83 conversion?
I think these should also be included to make the installation complete,
but if there is some problem then they can be omitted. The two-letter
files provide grid conversions with more precision than is available
from the normal grids. The modules don't currently use the high
precision files and I don't expect that the modules will use them until
there is some way of offering them to US users without also complicating
things for non-US users.
For what it's worth, there are quite a few high-precision conversion
grids that are available as of 10/17/01 that were not included in the
proj distribution. There is also a high-precision Canadian grid, but
when last I checked the high-precision Canadian data were only available
under a restrictive license. I expect that at some time in the future
the proj distribution will be updated to reflect the additional
high-precision grids. Probably only Frank would actually know.
Roger Miller