Format translator development

[David Irving]

Rich Shepard wrote:

> 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)
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Rich - and others -

imo, what is _really_ required is a MapInfo-to-<something> tarnslator together
with a <something>-to-GRASS translator, that is, use some common data format as
an interchange mechanism between any two spatial information systems. I believe
that there is a Standard for spatial data interchange, but have been unable to
get hold of a copy to assess whether it is actually useful. Any other approach
effectively means writing 2*N**2 data translation programs, where N is the
number of spatial data formats (large and growing all the time)

Regards,
David