[GRASS-user] How to draw the earthquake-magtintude map...

[Hamish]

Micha wrote:

sgw00412 wrote:
> I'm from Japan and begginer user of grass GIS.
> I tried to draw earthquake map of tohoku Japan.
...
> Next, I tried to display new map as circle size of earthquake-magnitude.
>  v.vect quake size=magnitude

you want to use 'd.vect quake size_column=magnitude'

size= sets a standard size for all points.


magnitude is not linear, nor really logarithmic, it's more like
 10^(11 + 1.5*m)   [rough approx!
so each whole numbers is ~ 31x more powerful than the previous.

IMHO presenting as linear is quite misleading.

You can find the scripts for Markus N. & my example PHP/batch job
earthquake map rendering[1] at the following links[2].

[1]
 http://adhoc.osgeo.osuosl.org/grass/alternate_projections/earthquakes_wintri.png
 http://adhoc.osgeo.osuosl.org/grass/archive/earthquakes_17March2011.png
 http://adhoc.osgeo.osuosl.org/grass/New_Zealand/earthquakes_NZ_ChCh.png
   (I felt this one quite well 2 days ago)
 http://adhoc.osgeo.osuosl.org/grass/archive/gns_Chch_quakes_sept2010_to_feb2011.png
 http://adhoc.osgeo.osuosl.org/grass/archive/gns_NZ_quakes_sept2010_to_feb2011.png
 http://adhoc.osgeo.osuosl.org/grass/recent_earthquakes_USGS.kmz


[2] code: (slightly out of date, I need to sync it..)
https://trac.osgeo.org/grass/browser/grass-promo/tutorials/batch_processing/earthquakes


Micha wrote:
> You probably want here:
>
> d.vect.thematic map=quake col=mag type=point \
>    themetype=graduated_points icon=basic/circle
>
> There are more options for coloring, etc.

I'm not a heavy user of d.vect.thematic, so I may be missing something,
but AFAIK thanks to new improvements to d.vect, the module is mostly
obsolete now. (or it could be greatly simplified to just the legend
generation stuff, and d.vect for the rest)


Hamish