Folks,
I have upgraded the proj library in my installation to version 4.5.5--it
may actually have been at that level to start with, I don't know. I
added some code to the library and modified r.proj, v.proj and s.proj to
perform the nad27<->nad83 datum change in a pretty seamless manner. For
our North American users, I'd like to get this capability into
GRASS5.0.0 before the feature freeze.
For now the datum shift is limited to the changes between the two nad
data. I hope the mechanism is sufficiently general that other datum
shifts can be added with relatively little change.
I need some help to get the changes installed in GRASS before the
feature freeze. My biggest problems are:
The nad27<->nad83 conversions are based on data tables. The data tables
are shipped in ascii form. They have to be interpreted to binary by a
program that ships with the package and then placed somewhere in the
$GRASSBASE hierarchy. Currently I have them in $GRASSBASE/etc/nad. It
would make more sense to me to put them in $GRASSBASE/lib/nad. Your
input would be appreciated.
The user modules must know where the data tables are stored, and that
information should be compiled into the modules. I think that would be
done by configure, but I don't know enough to say, much less enough to
make the change myself.
I don't know how to go about doing either of those tasks. Help?
I will also have to commit and/or add the library code. I think I can
figure that out.
There are some outstanding tasks.
I probably need to get the proj library list of projections in sync with
the GRASS 5 list.
At this point the modules are hardwired to perform the nad conversion
only in the conterminous US and adjacent areas and only at regular
precision. That needs to be changed. I would need either to install
the ability for the modules to determine which table they should use for
the input area or I need to make that an argument. Using the high
precision tables (maybe not necessary) would require another argument.
Added arguments make the datum change less seamless, so users outside NA
might find that annoying.
I have not upgraded m.proj to complete the datum change. I don't regard
that as a high priority.
Your input and help would be much appreciated.
Roger Miller