Getting Started
This plugin is designed to import and display isochrones (contours of fire progression) from FDS simulations in QGIS. It therefore requires that an FDS simulation has been run (see the qgis2fds plugin for an example of how to setup an FDS simulation in QGIS). To track the fire progression, the plugin requires that FDS outputs are stored in a terrain-following slice file. In your FDS file, this would looks something like:
&SLCF AGL_SLICE=5. QUANTITY='TIME OF ARRIVAL' /
The plugin will read the values from the slice output and convert these to isochrones. Currently supported values for QUANTITY are:
LEVEL SET VALUETIME OF ARRIVAL
However, TIME OF ARRIVAL is recommended as the values are computed at FDS run-time and will be more precise depending on the output frequency of LEVEL SET VALUE.
To use the fds_isochrones plugin in QGIS, make sure you have first installed it following these steps. You should then be able to load it from the Processing Toolbox and see a window which looks like this:
The plugin takes the following inputs:
| FDS case identifier (CHID) | Name given to the FDS case. |
| Working directory | Location of the FDS case (including *.out, *.smv, and *.slcf files). |
| CRS for FDS run | Coordinate reference system FDS case was run in. This determines how the domain XB values correspond to an extent on the globe. |
| FDS origin in CRS | Real word coordinates of the FDS origin (x,y)=(0,0). If ORIGIN_LAT and ORIGIN_LON were set for the FDS run then these values will automatically be loaded and it is not necessary to set an origin here. |
| AGL Slice QUANTITY | Output QUANTITY from FDS simulation, as described above. |
| Threshold QUANTITY | Value of QUANTITY which is indicative of fire arrival. For LEVEL SET VALUE this is 0. For TIME OF ARRIVAL it is not needed. |
| Contour intervals | Interval between isochrones drawn in QGIS (in seconds). Does not need to correspond to the output frequency of the slice file in FDS (DT_SLCF). |
| Filtered output resolution | If a value is provided, the contours will be computed from data re-interpolated and smoothed with a 3x3 box filter at the specified resolution. |
| Ignition time | Date and time of ignition/start of simulation. Used to animate the isochrones in QGIS, but can always be added or modified once they are created. |
| Save FDS sample points as temporary layer | Mostly used for debugging, this creates a vector layer of arrival time points at each FDS grid locations (this layer is then used to draw the isochrones). |
| Output layer | Location to save the output of the plugin. If not specified, the output will be added as a temporary layer and can be saved later. |
After running the plugin, the isochrones should be added to the project layers and look something like this:
