[GRASS5] Branching for 5.0.0 ahead

[rgrmill at rt66.com]

> > 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