[Qgis-user] proportional symbols

[G. Allegri]

Yes, it's very common, and in my field it's very useful too. For
example it is used to visualize wells water chemical monitoring...

2008/10/28 Goyo <goyodiaz at gmail.com>:
> It seems to be a more common feature than I thought. Still I don't
> understand the use if this (I think double size should mean double
> population) but I guess I can live with the clutter.
>
> Goyo
>
> El lun, 27-10-2008 a las 23:21 +0100, G. Allegri escribió:
>> It's very strange to me that it seams so strange to have proportional
>> point size symbology on the base of attributes values.
>> It's a basic feature of cartography...
>>
>> Some example references I can give:
>> http://mapserver.gis.umn.edu/docs/howto/cartosymbols/#scaling-of-symbols
>> http://demo.mapfish.org/mapfishsample/1.0/examples/geostat/proportionalSymbols.html
>> http://www96.reliefweb.int/tools/details/geospatial-analysis/symbols-and-markers
>>
>> 2008/10/27 Goyo <goyodiaz at gmail.com>:
>> > OK I read the ticket and I think I've got the point now. First of all
>> > you'll want to know that the lower size limit is gone in 1.0 but I don't
>> > think you're going to get good looking results with your data anyway.
>> >
>> > So you want to tell the sizes for maximum and minimum field values
>> > (whatever they are) and get the size for any value computed by linear
>> > interpolation.
>> >
>> > To be honest I don't see this useful enough (in general) as to justify
>> > the additional clutter in UI. On the other hand that's the way colormaps
>> > are handled in rasters, more or less.
>> >
>> > Just some thoughts.
>> >
>> > Goyo
>> >
>> > El lun, 27-10-2008 a las 21:49 +0100, Goyo escribió:
>> >> Hi Giovanny,
>> >>
>> >> it scales the symbol size, not the attribute values. Since your
>> >> attribute values are big you're getting big symbols.
>> >>
>> >> Goyo
>> >>
>> >> El dom, 19-10-2008 a las 21:15 +0200, G. Allegri escribió:
>> >> > I migrate here a discussion started in a ticket
>> >> > https://trac.osgeo.org/qgis/ticket/960
>> >> >
>> >> > I change the question asking the following: how to make proportional
>> >> > symbols, i.e. with the size based on a certain attribute?
>> >> > I thought I should use the "Area scale fields" in the Properties
>> >> > window. It does the work, but it doesn't scale the sttribute values,
>> >> > so if the they are "big" the symbols overlay each other even covering
>> >> > the entire screen.
>> >> >
>> >> > I show two images about this:
>> >> > Property dialog: http://www.geospatial.it/allegri/property.png
>> >> > Result: http://www.geospatial.it/allegri/graduated.png
>> >> >
>> >> > I've used the lower allowed "Dimension" (=3)...
>> >> >
>> >> > Am I using a tool that wasn't supposed to do this work? Or am I using
>> >> > it in the wrong way?
>> >> >
>> >> > Giovanni
>> >> > _______________________________________________
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>> >> > Qgis-user at lists.osgeo.org
>> >> > http://lists.osgeo.org/mailman/listinfo/qgis-user
>> >
>> >
>
>