[Qgis-developer] Multi threading and background processing

[Angus Carr]

r.los is based is based on the US Fire spread model (BEHAVE), or at least
it was a few years ago (10? 15? Augh!). It is not based on the Canadian
model (FBP).

The two models are significantly different in their parameters, and they
don't model the same things. For what it is worth, the r.los model models
the question "How long will fire take to spread from that other burning
neighbour cell to me?", so it ends up being an event-driven system, not a
time-driven system.

Having said that, it's a good point that looking at that code could be
informative.

I'm personally most interested in taking a page from the model built for
the prometheus project where they did the fire processing in a vector
model, which seems to reduce the nearest neighbour spread issue. They
published a paper on that, but I don't have it to hand. The idea was that
each point in a tiny circle around the start point would have a fire
prediction made, and then the assembled ellipses would be dissolved and the
new fire front would emerge as the collection of unique points on the
outside of the fire.

The topography and fuels are all straight point samples from rasters. The
weather is from a common hourly weather data set.

The advantage of the vector system is that the raster leads to strong pulls
in the direction of the raster grain (usually NS and EW). If you design it
for an 8-neighbour system, there are other effects. You could do a
six-neighbour system with a hexagonal "raster". All of them lead to effects
from the grain of the raster. These effects are exacerbated with a
time-driven system.

Anyway, I'm obviously off on a discussion that has a time and place
elsewhere... :-)

Cheers,
Angus.




On Thu, Nov 21, 2013 at 2:41 AM, Blumentrath, Stefan <
Stefan.Blumentrath at nina.no> wrote:

>  Hi Tom
>
>
>
> Besides the technical aspects, just in case you do not know them yet, you
> may probably get some scientific inspirations from e.g. r.los (and related
> modules) in GRASS (see http://grass.osgeo.org/grass64/manuals/r.ros.html)
> which represent existing GIS models for wildfire spread. Maybe something to
> build on…?
>
>
>
> Cheers
>
> Stefan
>
>
>
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