Data requirements¶
The Bushfire Attack Level Toolbox requires only two datasets to determine BAL – a classified vegetation dataset and a digital elevation model. With these two datasets, it is possible to determine the slope and aspect of a site, and the classified vegetation types described in AS 3959–2009, to enable determination of BAL.
Digital elvation model¶
A digital elevation model (DEM) is a digital model that represents a geographic location’s height above mean sea level. DEM’s are developed by a wide range of techniques, and have widely varying horizontal grid resolutions.
At the national scale, Geoscience Australia has published the 1-arcsecond Shuttle Radar Topography Mission (SRTM) Digital Elevation Models Version 1.0 (see http://www.ga.gov.au/metadata-gateway/metadata/record/gcat_72759), which is freely accessible. This DEM has a grid resolution of approximately 30 m by 30 m (at the equator). There are also other DEM’s available through the Geoscience Australia Data and Publications Search portal. Other organisations may have higher-resolution and more up-to-date DEMs available for use in the Bushfire Attack Level Toolbox.
For the Bushfire Attack Level Toolbox, it is recommended to use a DEM with a horizontal grid resolution comparable to the SRTM DEM (~ 30m), or higher for best results.
Format¶
Any raster format supported by ESRI ArcGIS 10.2 can be used in Bushfire Attack Level Toolbox. 32-bit floating point data in either GeoTIFF or the native ESRI Grid format is recommended.
Projection¶
The input DEM must be presented in a projected coordinate system, with a linear unit of metres. Projected coordinate systems such as Universal Transverse Mercator (UTM), or the Map Grid of Australia (MGA) are suitable for projecting elevation data for use in the Bushfire Attack Level Toolbox.
Warning
The Bushfire Attack Level Toolbox will fail to execute if the input DEM is in a geographic coordinate system.
For the western portion of Western Australia, the GDA94/MGA Zone 50 projection would be an appropriate choice of projected coordinate system.
Vegetation data¶
A classified vegetation dataset is required for determination of BAL. The availability of classified vegetation datasets is varied, and the classifications used are similarly diverse, depending on the application for which they were intended and the methods used to derive them.
For the examples used in this training workshop, we have used the National Vegetation Information System (NVIS), which provides information on the extent and distribution of vegetation types in Australian landscapes. This data has a horizontal resolution of 100 m by 100 m. Other organisations may have higher-resolution and more up-to-date classified vegetation datasets available for use in the Bushfire Attack Level Toolbox.
For optimal results, it is recommended to use a classified vegetation dataset that is of a comparable resolution to the DEM used.
Format¶
Any raster format supported by ESRI ArcGIS 10.2 can be used in Bushfire Attack Level Toolbox. Generally, an unsigned integer data type will be sufficient to describe the classified vegetation type. Either GeoTIFF or the native ESRI Grid format is recommended.
Classification¶
The vegetation data needs to represent different classification types. Ideally, the data will match the vegetation classes set out in AS 3959–2009. These are numbered 1–7 and are defined as follows:
| Value | Classification | Description |
| 1 | Forest | Tall, open forest, tall woodland, open forest, low open forest, pine plantation |
| 2 | Woodland | Woodland, open woodland, low woodland, low open woodland, open shrubland |
| 3 | Shrubland | Closed heath, open heath, low shrubland |
| 4 | Scrub | Closed scrub, open scrub |
| 5 | Mallee/Mulga | Tall shrubland |
| 6 | Rainforest | Tall closed forest, closed forest, low closed forest |
| 7 | Grassland | Low open shrubland, hummock grassland, closed tussock grassland, tussock grassland, open tussock, sparse open tussock, dense sown pasture, sown pasture, open herbfield, sparse open herbfield |
Warning
The input data must be in this numerical format for the Bushfire Attack Level Toolbox to execute correctly. Values other than those listed here will be ignored and may produce incorrect BAL values.
The Bushfire Attack Level Toolbox provides users with the option to map their classified vegetation to the required classes. By default, the mapping matches the numerical values from NVIS to the required AS 3959–2009 values.
Projection¶
The input classified vegetation dataset should be presented in a projected coordinate system, with a linear unit of metres. Projected coordinate systems such as Universal Transverse Mercator (UTM), or the Map Grid of Australia (MGA) are suitable for projecting elevation data for use in the Bushfire Attack Level Toolbox.
Note
The vegetation dataset can be in either a geographical or a projected coordinate system. It will be reprojected to the same projection and same resolution as DEM by the BAL tool.
For the western portion of Western Australia, the GDA94/MGA Zone 50 projection would be an appropriate choice of projected coordinate system.