Format translator development

[Rich Shepard]

On Sat, 13 May 2000, David D Gray wrote:

> The problem with these others is that they mostly import lines in the
> originating application's native format. Often that means closed loops. Is
> that the case with MapInfo? If it was, I think that some kind of engine
> for translating the MapInfo format to GRASS arc-node would be required. Is
> that what you meant?

David,

  I don't know. The MapInfo export format for points and lines is
straight-forward: for points, the position and the symbol descriptor; for
lines, the number of segments in the line then the position for each node.
The MapInfo region (everyone else's polygon) is a closed line with one or
multiple segments. What's interesting, of course, is that MapInfo does not
build or maintain topology. For soil polygons, for example, each soil type
is its own polygon and the common lines aren't, there's one line for each
polygon.

> Because there are so many formats that require these changes on import, I
> am coming round to the conclusion that there should be some kind of
> translation engine in the main GRASS lib (to economise on code space and
> streamline module development), perhaps like the methods incorporated in
> the shapefile import - but more modular, efficient and cleaner of course
> -...

  Now that I think about it, I agree. I need to understand the arc-node data
structure's relationship to a closed polygon before I can write the
MapInfo-to-GRASS translator. Of course, if you or anyone else with more
experience in GRASS formats is willing to undertake this task, I'll be happy
to relinguish it. But, I will certainly answer any questions regarding the
MapInfo format. 

Rich

Dr. Richard B. Shepard, President

                       Applied Ecosystem Services, Inc. (TM)
              Making environmentally-responsible mining happen. (SM)         
                       --------------------------------
            2404 SW 22nd Street | Troutdale, OR 97060-1247 | U.S.A.
 + 1 503-667-4517 (voice) | + 1 503-667-8863 (fax) | rshepard at appl-ecosys.com