Thanks Alan ;-)
I often find email so infuriating. This thread, in person, would have been a 2 minute conversation. I just want to make sure I get a good feel for what the devs and community want before I spend too much to much time coding, especially if, like this, it's a moderate sized change. And the discussion has been useful - I'll certainly attack this differently now than I would have if I hadn't asked the questions.

I wonder if the speed has something to do with ignoring features below or close to the resolution of the map. I imagine that GIS software has to be cleverer about this kind of thing than we will need to be (and cleverer than I intend to try to be - As Andrew says PLplot isn't GIS software).

Anyway I've been scratching my head over the linebreak patch that Andrew has been looking at. Hopefully if this is sorted soon I'll be able to put it to bed and spend some time on the maps.


From: Alan W. Irwin <>
To: phil rosenberg <>
Cc: "" <>; Andrew Ross <>
Sent: Friday, 5 October 2012, 21:38
Subject: Re: [Plplot-devel] map resolution

By the way, I looked for a shapefile viewer on Debian and found
thuban. I don't know whether that is the best shapefile viewer for
Linux, but it is based on libgda/ogr.  When I tried thuban on overall
shapefile maps for British Columbian (obtained by following links at it appeared to work instantaneously
and well for the size (which totalled 200MB) of the 7 shapefile layers
making up the map of British Columbia that is provided by  Furthermore, I was much impressed
with all the high-resolution local detail (e.g., coastlines, natural features,
political boundaries to name three of the most useful shapefile layers
available for the British Columbia map) that was available under the
thuban zoom mode.  By the way, that zoom mode worked essentially
instantaneously as well.

I assume shapelib will be as fast or faster than libgda/ogr so I think
we have a lot to look forward to concerning the speed with which
shapelib can deliver shapes behind the scenes to plmap for that
function to plot.

And to anticipate a possible ( :-) ) further question from Phil, no I
don't think we should get into trying to let plmap deal with several
shapefile file layers at once. Instead it should be the users'
responsibility to specify, e.g., "british_columbia_coastline.shp" as a
filename to plmap if they want the B.C. coastlines on their plot, and
if a user wants another layer in their plot with natural features on
top of those coastlines, they can call plmap again with a different
filename for the same region, e.g., "british_columbia_natural.shp".

Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (

Programming affiliations with the FreeEOS equation-of-state
implementation for stellar interiors (; the Time
Ephemerides project (; PLplot scientific plotting
software package (; the libLASi project
(; the Loads of Linux Links project (;
and the Linux Brochure Project (

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