[GRASS5] [OFFTOPIC] Need some help...

[Dmitry Suzdalev]

Thanks, Roger! 
I'll look into it!

On Wednesday 21 December 2005 11:19, Roger Bivand wrote:
> A lightweight approach is to decimate the long-lat data first - I think
> the code at:
>
> ftp://gmt.soest.hawaii.edu/pub/pwessel/gshhs
>
> is pretty informative (or was until I tried it now - seems to be down
> temporarily - look for gshhs.h, gshhs.c, and especially gshhs_dp.c,
> which contains the line simplification code - looks as though they are
> copied in:
>
> http://www.ngdc.noaa.gov/mgg/shorelines/data/gshhs/version1.3/gshhs_1.5_src
>.zip
>
> ).
>
> In fact, my first cut on your task would have been to use GMT straight
> off, pushing the projected output Postscript into gs or some such to
> render to your window. Depending on the size of your window, the
> pre-thinned coarse or low GSHHS datasets might be good enough, but I don't
> know if you need more features than just shorelines.
>
> > Daniel.
> >
> > On 12/20/05, Dmitry Suzdalev <dimsuz at mail.ru> wrote:
> > > Hi, dear GRASS developers :).
> > > Please, sorry for maybe offtopic, but I have one question.
> > > I'm learning my way into world of map projections and my task is to
> > > display all the world in a GUI window (QT-window, actually).
> > > I've already managed to do it, using libproj4 :).
> > > But... There is sooo much data to be displayed that it draws rather
> > > slow.
> > >
> > > And it's obvious, that it's not needed to draw EACH map data primitive,
> > > because some of them are so small, that they're represented by one
> > > pixel, when using large scales. And still, if I have 1000 primitives
> > > (polylines, regions etc) that are so small, that they fit in one
> > > concrete pixel, they'll all be drawn. In the same pixel. 1000 times.
> > > That's slow :).
> > >
> > > So the question is: is there any common algorithm to cope with this
> > > situation? Which helps to somehow "filter out" the primitives which are
> > > represented by a single pixel at the screen and draw that pixel only
> > > once?
> > > Or should i investigate that algorithm by myself? :)
> > >
> > > Again, sorry if this is offtopic, I've googled for a few hours trying
> > > to find some kind of web-forum for such kind of questions, but I didn't
> > > find it :). Googling on "gis developers forum" pointed me to your
> > > mailing list, so I decided to give it a try :).
> > >
> > > Maybe at least, you can point me to the right place to ask such a
> > > question? :)
> > >
> > > Thanks in advance!
> > >
> > > And sorry for my maybe not very good English ;).
> > > Cheers, Dmitry.
> > >
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> >
> > --
> > -- Daniel Calvelo Aros
> >
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