HOTSPOT service specifications

This service takes in input optical multispectral data given in native format and employs an hotspot detection algorithm based on nir and swir22 spectral bands to generate a bitmask of active fires.

HOTSPOT requires in input Optical EO data in native format. The optical calibration is handled as pre-processing within the service.

Service Description

The Hotspot Detection (HOTSPOT) service employs an hotspot algorithm that requires in input optical EO data in native format having at least nir and swir22 assets (e.g. for Sentinel/2 MSI those are respectively the 8A and 12 bands). Input optical EO data must be given in native format. It calculates the ratio and the difference between those assets in TOA reflectance:

Pixels over water are masked and then excluded from the hotspot detection in case of TOA reflectance for swir22 asset is minor than 0.04. Hotspot and candidate hotspots are then identified using the following expressions:

The algorithm performs a background characterization around candidate hotspot pixels in case of a large fire event. The aggregated hotspot size is increased if the number of candidate fire pixels is less than the half of the total pixels in the window (approximately 2x2 km). Statistics (mean and standard deviation of the ratio) are also computed for pixels within the windows considered in the background characterization. In a later stage, the algorithm undertakes contextual tests which are needed to decide for all candidate hotspot pixels if they can be classified as hotspot or not.

In this process, two conditions needs to be satisfied to classify a candidate pixel as hotspot:

1. ratio > ratio_mean + max((3 * ratio_std), 0.5),

2. swir22 > swir22_mean + max((3 * swir22_std), 0.05).

Finally, the algorithm returns the hotspot classification of the entire scene as a binary mask (No-Fire=0, Hotspot=1). Output binary classification file is given as GeoTIFF in COG format.

Input

This processor uses as input a calibrated product from the Optical Products having swir22 and nir STAC assets.

Examples of such missions are:

• Sentinel-2
• Landsat-8

Parameters

The HOTSPOT service requires a specified number of mandatory and optional parameters. All service parameters are listed in the table below.

Table 1 - Service parameters for the HOTSPOT processor.

Output

This processing service generates the outputs described below:

Vectorize HOTSPOT single band asset

HOTSPOT's binary mask can be converted to polygons by using the FilterVectorize service in Vectorize mode and selecting only true values DN=1 (hotspot).