I think the aim is exactly that, to FIND the radius for each biogas plant
which is able to provide the plant with enough resources.
I once had a quite similar problem, to create new polygons which had to
reach a certain sum value of credits per unit, but overlaying other
polygons with different credit values.
My semi-optimal solution was to "rasterize" the polygons to a vector grid.
I then selected the grid cells and used a statistics plugin to sum up the
credits until I reached the desired amount, and then saved the selection
as a new feature. The Live Statistics plugin could be used for that.
It really depends on how many plant points you already have. If they are
many, this will be a tedious and boring job and you better might find
someone to code a little python script.
If I had the abilities, I would code something like this:
Rasterize your polygons to a vector grid with your gas potential value (so
if grid size is hectares, then simply your value)
Iterate over your point layer:
x = plant gas consuption
select cell underneath point 1
y = cell gas potential
set cell value to 0 (your "vacuum")
select next cells circularily around the first and add cells values to y
until y >= x
copy selected cells, dissolve them and save as a new feature in a new layer
next point
Once wanted to code sth like this in R, but I'm sure there are many people
with PYQGIS-abilities who could do sth like this easily.
Could maybe even better work with real raster ... no idea.
Cheers
Bernd
Am 03.07.2015, 14:45 Uhr, schrieb Kristian Evers <kr...@gst.dk>:
Hi Julie.
You need to define a surrounding area for each of the biogas plants. I
suggest you base the >surrounding areas on the polygons you already
have, so that each plant has a polygon that is a union >of several
surrounding biogas-potential polygons. How to do this is up to you.
Hereafter you can select all potential-polygons that intersect the
plant-polygons and sum up the >potentials within each of the
plant-polygons.
I hope that was enough to bring you on the right track.
Kristian
Fra: qgis-user-boun...@lists.osgeo.org
[mailto:qgis-user-boun...@lists.osgeo.org] På vegne af Julie Houge Hansen
Sendt: fredag 03. juli 2015 13:35
Til: qgis-user@lists.osgeo.org
Emne: [Qgis-user] Vacuuming a vector polygon layer with a point layer in
QGIS 2.8.2 (windows)
Dear all
I have tried asking my local QGIS expert but unfortunately she is for
once not able to help me. I >hope someone can.
- I have a vector polygon layer that contains data for the
amount of biogas potentially available >in a polygon - unit is
m3/ha/year. The polygons are of varying size.
- I have another vector point layer with data for the amount of
biogas already produced on >specific biogas plants – unit in m3/year.
- I would like to combine the two layers so that I “vacuum” the
area surrounding the biogas >plants for biogas potential. This will
reveal where there are still areas with sufficient >biomass available
for a new biogas plant to be build.
I have no clue how to do this calculation but I think it should be
possible. Can anyone help me out?
The overview I have of my data now looks like this:
The size of the shown point data is independent on the polygon layer. I
would like it to be dependent >on the biogas potential available (in the
polygon layer). I would like the size of the points to >reflect how far
you would have to drive (radius to the biogas plant) in order to get all
the biomass >needed to produce the biogas you intend to.
I am using QGIS version 2.8.2 64 bit with Windows.
Best regards
Julie Houge Hansen
PhD Student, Inst. of Chemical Eng., Biotechnology and Environmental
Tech.> >
Tlf.
+4565507212
Email
j...@kbm.sdu.dk
Addr.
Niels Bohrs Allé 1, DK-5230 Odense M, Denmark
Campusvej 55 · 5230 Odense M · Tlf. 6550 1000 · www.sdu.dk
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