[Opengrads-devel] Shapefile extension: first crack

[Arlindo da S. <da...@al...>]

Graziano,

   I have an initial implementation of your shapefile "draw polyf"
implemented as a GrADS extension. Just check out the Grads module

% gacvs co Grads
% cd Grads/extensions/shape
% make
% perldoc shape
% setenv GAUDXT ./shape.udxt

For convenience I have incorporated libshp with the sources, at least
for now. Look at file utShape.gs for an example. You will need the
gshhs_land.??? files for running this test, and a GrADS build
supporting UDXTs. You should be able to build the sources you just
checked out.

A few comments:

1) I rearranged your code a bit, grouping together portions that could be reused

2) I added "shp_lines" for my own benefit, it may not be needed in the end as
polyf should handle non-closed polygons as well. At this point,
though, they do not produce the same output.

3) I am not sure whether "shp_polyf" works as you intended. The
polygon fills look funny.

4) The current sources let GrADS handle clipping. Your old function
NormalLon (renamed here StdLon) and the InsideDomain() functions are
effectively disabled. You may have good reasons for re-enabling them.

5) The documentation needs to be filled in.

6) It would be nice to have a nice set of simple examples, with small files.

7) It appears to me that one should be able to write shapefiles with
the contents of
the GrADS "metafile" (with coordinates expressed in lat/lon which I
believed can be accomplished with the appropriate conversion). I went
ahead and put in the skeleton from my "gxyat" extension which grabs
the metafile buffer from memory and translates it. This work would be
better completed by someone with shapefile familiarity. Better yet,
with means of testing it. I have no experience (or personal interest
for that matter) in GIS software, but I realize it would be important
to reach out to the GIS community. Any volunteers to take this on? (I
can help with the metafile translation if needed.)

Efren: have you been able to make progress in this area?

  Please let me know if you have any comments.

     Arlindo

-- 
Arlindo da Silva
da...@al...