[Qgis-user] Organic heatmap outter contour, and making it look better

Mon Jul 27 10:16:36 PDT 2015

Brent,

Thanks a lot for the reply!

That's a lot of valuable information packed in a few paragraphs! There are
a few points I didn't fully understand yet, I hope you don't mind me asking
a few more questions:

surface, triangulate, xyz2grd, greenspline can all generate a grid from
> scattered point data, depending just how you want it done

I'm really just beginning with GIS visualizations. If I can get something
close to what I've shown in the first message:

1) This http://i.stack.imgur.com/DvVyU.png (with outer edges clipped to the
radius contours);
2) Or this
https://www.dropbox.com/s/9ig76n1kcxoo76w/Screenshot%202015-07-24%2021.39.00.png?dl=0
;
3) Or
http://www.gislounge.com/wp-content/uploads/2014/08/fortune1000-heat-kernel-us.png
.

..I'll be happy. The high-level question I have now is: What would be the
minimum set of tools, settings andI need to create a viz. like this from a
set of point with a lat, lon and weight value? (value-based, based off the
weight and another one based off the density of points) ... specific
questions follow:

gridhisteq can normalise it if required

What do you mean by normalise? When would be this needed?

grdimage will turn it into a postscript image

Why postscript?

ps2raster will turn it into a georeferenced png

Interesting, why is this needed specifically? For WMS?

if you want to clip it to a contour, you can use psclip, or you can use a
> colour palette to set cells >representing certain values to NA, & render
> them as transparent

Perfect! Yes, I want to the outer edges to follow a organic 'flow', and not
crop like the example I sent. Thanks for pointing me out to psclip. Do you
know/Could point me to an example/tutorial of how to use it / or the colour
palette technique to get the viz. I'd like?

Thanks again,

-- Marcelo.

On Sat, Jul 25, 2015 at 10:47 PM, Brent Wood <pcreso at pcreso.com> wrote:

> Generic Mapping Tools (http://gmt.soest.hawaii.edu) can do all you want,
> fully scripted:
>
> surface, triangulate, xyz2grd, greenspline can all generate a grid from
> scattered point data, depending just how you want it done
> gridhisteq can normalise it if required
> grdimage will turn it into a postscript image
> ps2raster will turn it into a georeferenced png
>
> if you want to clip it to a contour, you can use psclip, or you can use a
> colour palette to set cells representing certain values to NA, & render
> them as transparent
>
> you can then provide it as a WMS layer with mapserver, qgis server or
> geoserver
>
> See sections 7.14-7.19 here:
> http://gmt.soest.hawaii.edu/gmt4/gmt/html/GMT_Docs.html
>
> GDAL may be adequate, but has a more limited set of gridding &
> cartographic tools, and GRASS can also do what you want.
>
>   ------------------------------
>  *From:* Marcelo de Moraes Serpa <celoserpa at gmail.com>
> *To:* qgis-user <qgis-user at lists.osgeo.org>
> *Sent:* Saturday, July 25, 2015 3:13 PM
> *Subject:* Re: [Qgis-user] Organic heatmap outter contour, and making it
> look better
>
> Ops, forgot to include the reference heatmaps here. The goal is to get it
> to look +- like the ones below:
>
> *
> http://www.gislounge.com/wp-content/uploads/2014/08/fortune1000-heat-kernel-us.png
> and/or
> * http://i.stack.imgur.com/DvVyU.png
>
> Cheers,
>
> -- Marcleo.
>
>
>
> On Fri, Jul 24, 2015 at 9:58 PM, Marcelo de Moraes Serpa <
> celoserpa at gmail.com> wrote:
>
> Thanks to @Neumann, @Abdishakur and @Richard from my previous thread, the
> info was valuable! I did reply the post with some additional questions it
> but for some reason the mailing list server bounced my messages. They are
> not so relevant anymore, but if you get them, I'd still want to know your
> opinions.
>
> Anyway, I played a couple of hours today with the data I have and with the
> interpolation and countours features of QGis (which seems to use Gdal under
> the cover, which was, for me, a quite interesting finding! That means that
> any result I get with QGis could easily be scriptable, which is  a must,
> since it will eventually be used in a web app pipeline) and I got this:
>
>
> https://www.dropbox.com/s/9ig76n1kcxoo76w/Screenshot%202015-07-24%2021.39.00.png?dl=0
>
> It still doesn't look quite like I want*[0] but I'm getting there. The
> countours feature seems to be what I want. The numbers, by the way, is
> revenue per day in a certain area. The colors are not quite right (too many
> of them) so I need to tweak the styles, I think, and I don't want the
> actual countours lines to appear. They all seem to be simple problems to
> solve, but if you know how to do them, I'd love to know!
>
> What seems to be more complicated, is how to create an organic feeling to
> the map. I don't want it to be a square, like this, I want the edge to
> follow the outter points. Here's what I mean:
> https://www.dropbox.com/s/k6na766a4ox1ngg/Screenshot-2015-07-15-21.47.55.jpg?dl=0.
> Does anyone have any idea of to do this?
>
> Thanks!
>
> -- Marcelo.
>
>
>
>
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