This article provides a deep dive into the data that Nearmap Fire Risk AI delivers, which will help you understand the data and arrive at an assessment of the level of fire risk for a property.
NOTE: We recommend that you cross-check the results from this with MapBrowser imagery or imagery from another source. For more information, see Statistical Performance.
Defensible space refers to the area that is created between a building on your property and a contour that is drawn at particular distance, such as:
- 0 to 5 ft
- 0 to 10 ft
- 0 to 30 ft
- 0 to 100 ft
- 0 to 300 ft.
The distance is based on imagery from the latest Nearmap surveys. Based on the specific attributes that are detected within the defensible space, such as vegetation, water body, etc, you can assess the fire risk for a property. For other attributes, such as pole, the output will include the count instead.
This output type is available to US and AU customers.
Data insight: The proximity of an attribute to a property (combined with other aspects such as slope and elevation) has a direct impact on the fire risk. For example, high vegetation near a property might increase fire risk while the presence of a water body may mitigate that risk.
Defensible space attributes
Nearmap assesses the presence of attributes over five distance zones up to 300 ft as well as overlap with the building itself. The zones include:
- 0 to 5 ft
- 0 to 10 ft
- 0 to 30 ft
- 0 to 100 ft
- 0 to 300 ft
NOTE: Nearmap calculated zones include distances used commonly in the industry, as well as additional levels to add more granularity and risks over greater distances. The zone numbering is Nearmap specific and the mapping for zone number to distance ranges varies in the industry.
Nearmap assesses the presence of the following attributes:
Data from the following 3D topographic features used in conjunction with the AI attributes allows you to make an informed and accurate assessment about the fire risk for a property.
- Terrain Ruggedness Index (TRI)
- Terrain Position Index (TPI)
3D topography data
Before we describe the Fire Risk data we provide, let's look at the source of the 3D topography data and other important information about this output data type.
- 3D topography data is sourced from 3D Elevation Project (3DEP) . The United States Geological Survey, which is the lead agency for the collection of elevation data in the United States, has been working on 3DEP since 2012. Under this project, the USGS has been gathering additional elevation data from a variety of sources, predominantly light detection and ranging (LIDAR).
- The data above is processed on our AI pipeline where we apply some proprietary calculations.
- This data is not updated frequently. We will update our data annually to sync with the source date; However, we cannot guarantee the frequency of updates on the source data from 3DEP.
- On the API, we will always return the latest available data from 3DEP regardless of the date parameter entered by the user.
NOTE: 3D topography data is only available for US customers.
Aspect is the direction in which the plane of the slope faces.
Data insight: In the Northern hemisphere, south-facing aspect is typically hotter and drier. Therefore, wildfires tend to start more easily and spread faster.
Slope is the steepness of a surface, defined as rise over run. At a particular location, it is the steepest slope value calculated using adjacent pixels, i.e. the gradient of the elevation. For slope values at different spatial scale to the 3DEP resolution (e.g. for directional slope), we first calculate the pixel slope value, and then calculate the average.
Data insight: Fire tends to travel more rapidly up a hill - for every 10 degrees of slope, a fire can double its speed. Therefore, buildings on steeper slope can have greater wildfire risk.
Elevation is the bare earth DEM derived from the 3DEP 1/3 arc-second seamless dataset. The source data was re-projected to EPSG:4326 (pseudomercator) for compatibility with other Nearmap data.
Data insight: Elevation can affect temperature and climate, vegetation types, fuel moisture content and fire spread.
Terrain Ruggedness Index (TRI)
TRI is the average deviation between adjacent elevation pixels and the central elevation pixel. TRI at different spatial resolution captures different terrain features. Here, we provide TRI at 100ft and 300ft buffers.
Data insight: On rugged terrain, fires can spread erratically, driven by wind direction and other weather patterns. Rugged terrains tend to be difficult to access and hard for firefighters to extinguish fires.
Terrain Position Index (TPI)
TPI is the difference between the central elevation pixel and the average of the surrounding elevation pixels. TPI is a relative measure of a location’s elevation with respect to its surroundings. A positive TPI can indicate the pixel is centered on a hill or a ridge, and a negative TPI can indicate a valley.
Data insight: Fire behaviour can be influenced by terrain features such as ridges or valleys.
For instructions on how to access Nearmap Fire Risk AI data, see Access Nearmap Fire Risk AI Data.
Data from the following auxiliary sources used in conjunction with the AI attributes will allow you to make an informed and accurate assessment of the fire risk for a property.
- Wildland-urban interface (WUI)
- Wildfire Hazard Potential for the United States (WHP)
Auxiliary risk data
Auxiliary risk data is sourced from:
- Wildland-urban Interface (WUI) - This dataset captures areas where urban development occurs in proximity to wildland vegetation in continental United States.
- Wildfire Hazard Potential (WHP) for the United States - This dataset measures the risk of occurrence of wildfire in the United States. It is generated from the LANDFIRE 2014 dataset (so it reflects landscape conditions at the end of 2014), simulations and historical wildfire records.
The data above is processed on our AI pipeline where we apply some proprietary calculations. We update our data annually to sync with the source data; however, we cannot guarantee the frequency of updates on the source data from WUI and WHP.
On the API, we will always return the latest available data from WUI and WHP regardless of the date parameter entered by the user.
NOTE: Auxiliary risk data is only available for US customers.