Ignitions - Minimum Travel Time Fire Spread (MTT) Input

ignition field in MTT with a drop-down menu populated with shapefile names.

Once your landscape is selected, use a shape or shapefile to indicate the location and pattern of ignition on the landscape.

You must select your landscape prior to selecting an Ignition file. Available files are limited to:

  • Shapes you’ve created in IFTDSS or shapefiles you’ve uploaded. Points, lines, and polygons are all available as ignitions.

  • Shapes or shapefiles that intersect your landscape, or the buffered area surrounding it.

  • A single shape or shapefile. The file may be single or multipart.

Important! Ignitions and barriers must be at least one cell width away from each other or the model run will fail.

Once a shape or shapefile is selected for the ignition input, it may not be used for the barrier input.

Using Polygons

Polygons may be used to represent ignitions. Be aware of the information below to successfully model using this ignition type:

Important! To avoid run failure or misinterpretation when using polygons:

  • Be aware MTT Fire Spread treats the area within the polygon as non-burnable, fire is not permitted to burn inward.

  • Do not use ignition files that land completely in unburnable fuels or within a barrier, these will cause a run failure.

Resolution and Raster Conversion

The Minimum Travel Time Fire Spread (MTT) model is a raster based model that converts ignition and barrier vectors to rasters prior to the model running. Point and line ignitions will default to the same width as the cell resolution of your landscape.

The images below show a before (image A) and after (image B) example of lines and polygons being converted to raster format.

  1. Image A shows two vectors, a line used for ignition (orange) and a polygon used for a barrier (green), that were entered as inputs for a MTT run.

    ignition line (orange) and barrier polygon (green) shown on the landscape.

  2. Image B shows those same inputs after they have been converted to grid format for running MTT.

    raster versions of an ignition point and line (orange) and barrier polygon (green). A box on the right highlights the fact that a raster point may be larger than the vector version of that same point

Creating an Ignition While Using the MTT Fire Spread Interface

In Split Screen, you may create points, lines, and polygons at anytime in the map interface and these features will automatically become available in the drop-down menus for the Ignition and Barrier inputs. This includes creating a shape, uploading a shapefile, creating a shapefile subset from the Layer List widget, or from the Attribute Table. Split Screen is the default display mode for MTT.

Split screen mode showing MTT input fields on the right and Map Studio with widgets on the left.