Automatic detection of fires on earth's surface and of atmospheric phenomena such as clouds, veils, fog or the like, by means of a satellite system

• US 8,594,369 B2
• Filed: 01/17/2013
• Issued: 11/26/2013
• Est. Priority Date: 07/28/2006
• Status: Active Grant

• Current Assignee: Telespazio SPA (Leonardo S.p.A.)
• Original Assignee: Telespazio SPA (Leonardo S.p.A.)
• Inventors: Zavagli, Massimo, Constantini, Mario
• Primary Examiner(s): Zarka, David
• Assistant Examiner(s): YENTRAPATI, AVINASH
• Application Number:
  US13/743,506
• Publication Number:
  US 20130129147A1
• Time in Patent Office: 313 Days
• Field of Search: None
• US Class Current: 382/100
• CPC Class Codes: G06V 10/25 Determination of region of interest [ROI] or a volume of interest [VOI]
• CPC Class Codes: G06V 20/13 Satellite images

Abstract

A method is provided for automatically detecting fires on Earth'"'"'s surface by satellite. The method includes: acquiring multi-spectral images of the Earth at different times, each a collection of single-spectral images each associated with a respective wavelength, each image being made up of pixels each indicative of a spectral radiance from a respective area of the Earth; computing an adaptive predictive model predicting spectral radiances at a considered time for considered pixels based on previously acquired spectral radiances of the considered pixels and those previously predicted for the considered pixels by the adaptive predictive model; comparing acquired spectral radiances of the considered pixels at a considered time with those predicted at the same considered time for the considered pixels by the adaptive predictive model; and detecting fires or atmospheric phenomena in areas of the Earth'"'"'s surface or atmosphere corresponding to the considered pixels based on an outcome of the comparison.

Claims

1. A method for automatically detecting fires on Earth'"'"'s surface and atmospheric phenomena in Earth'"'"'s atmosphere by means of a satellite system, the method comprising:

acquiring multi-spectral images of the Earth at different times by means of a multi-spectral satellite sensor, each multi-spectral image being a collection of single-spectral images each associated with a respective wavelength (λ

), each single-spectral image being made up of pixels each indicative of a spectral radiance (R_λ

) from a respective area of the Earth;

computing an adaptive predictive model predicting spectral radiances (R_PRD,λ

) at a considered time for considered pixels on the basis of previously acquired spectral radiances (R_λ

) of the considered pixels and of spectral radiances (R_PRD,λ

) previously predicted for the considered pixels by said adaptive predictive model;

comparing acquired spectral radiances (R_λ

) of the considered pixels at a considered time with spectral radiances (R_PRD,λ

) predicted at the same considered time for the considered pixels by the adaptive predictive model; and

detecting a fire in areas of the Earth'"'"'s surface or an atmospheric phenomenon in areas of the Earth'"'"'s atmosphere corresponding to the considered pixels on the basis of an outcome of the comparison, wherein computing an adaptive predictive model includes;

computing, for each considered pixel, a temporal harmonic analysis of the spectral radiances of the pixel related to different times, and acquired at, or predicted for the same wavelength (λ

); and

computing the adaptive predictive model based on computed low-frequency components of the spectral radiances so as to filter out high-frequency changes in the spectral radiances due to fires on Earth'"'"'s surface or atmospheric phenomena, wherein computing, for each considered pixel, a temporal harmonic analysis includes;

forming a vector (λ

) containing the spectral radiances related to different times, and acquired at or predicted for the same wavelength (λ

); and

computing the temporal harmonic analysis of the vector (h_λ

)

classifying as valid or invalid acquired spectral radiances (R_λ

) according to a given criterion;

and wherein forming a vector (h_λ

) further comprises;

updating the vector (h_λ

) with the acquired spectral radiances (R_λ

) if they are classified as valid or with the corresponding predicted spectral radiances (R_PRD,λ

) if the acquired spectral radiances (R_λ

) are classified as invalid.

2. The method of claim 1, wherein the temporal harmonic analysis is a Fourier analysis.

3. The method of claim 1, wherein detecting a fire in an area of the Earth'"'"'s surface or an atmospheric phenomenon in an area of the Earth'"'"'s atmosphere corresponding to a considered pixel comprises:

detecting an atmospheric phenomenon if the acquired spectral radiance (R_λ

) of the pixel is lower than the corresponding predicted spectral radiance (R_PRD,λ

) of a given threshold value (th_DET,λ

); and

detecting a fire if the acquired spectral radiance (R_λ

) of the pixel is higher than the corresponding predicted spectral radiance (R_PRD,λ

) of a given threshold value (th_DET,λ

).

4. The method of claim 3, wherein an atmospheric phenomenon is detected in an area of the Earth'"'"'s atmosphere corresponding to a pixel by using the adaptive predictive model, the acquired spectral radiance of the pixel (R_10.8) and the threshold (th_DET,10.8) associated with the 10.8 μ

m wavelength or by using the adaptive predictive model, the acquired spectral radiance of the pixel (R₁₂) and the threshold (th_DET,12) associated with the 12 μ

m wavelength; and

wherein a fire is detected in an area of the Earth'"'"'s surface corresponding to a pixel by using the adaptive predictive model, the acquired spectral radiance of the pixel (R_3.9) and the threshold (th_DET,3.9) associated with the 3.9 μ

m wavelength.

5. The method of claim 1, wherein forming a vector (h_λ

) comprises;

forming an initial vector (h_λ

) containing spectral radiances (R_λ

) of the considered pixel acquired at the same wavelength (λ

) and at different times and not affected by fires, clouds, veils, fog or the like.

7. The method according to claim 1, wherein updating the vector (h_λ

) comprises;

replacing in the vector (h_λ

) the spectral radiances at given times with the corresponding acquired spectral radiances (R_λ

) classified as valid or with the corresponding predicted spectral radiances (R_PRD,λ

).

15. A processor in communication with the sensor configured to implement the method according to claim 1.

16. A software stored on a non-transitory computer readable medium and loaded in a processing system and configured to implement, when run, the method according claim 1.

6. A method for automatically detecting fires on Earth'"'"'s surface and atmospheric phenomena in Earth'"'"'s atmosphere by means of a satellite system, the method comprising:

acquiring multi-spectral images of the Earth at different times by means of a multi-spectral satellite sensor, each multi-spectral image being a collection of single-spectral images each associated with a respective wavelength (λ

), each single-spectral image being made up of pixels each indicative of a spectral radiance (R_λ

) from a respective area of the Earth;

computing an adaptive predictive model predicting spectral radiances (R_PRD,λ

) at a considered time for considered pixels on the basis of previously acquired spectral radiances (R_λ

) of the considered pixels and of spectral radiances (R_PRD,λ

) previously predicted for the considered pixels by said adaptive predictive model;

comparing acquired spectral radiances (R_λ

) of the considered pixels at a considered time with spectral radiances (R_PRD,λ

) predicted at the same considered time for the considered pixels by the adaptive predictive model; and

detecting a fire in areas of the Earth'"'"'s surface or an atmospheric phenomenon in areas of the Earth'"'"'s atmosphere corresponding to the considered pixels on the basis of an outcome of the comparison, wherein computing an adaptive predictive model includes;

computing, for each considered pixel, a temporal harmonic analysis of the spectral radiances of the pixel related to different times, and acquired at, or predicted for the same wavelength (λ

); and

computing the adaptive predictive model based on computed low-frequency components of the spectral radiances so as to filter out high-frequency changes in the spectral radiances due to fires on Earth'"'"'s surface or atmospheric phenomena and wherein forming an initial vector (h_λ

) comprises;

forming an initial vector (h_λ

) containing spectral radiances (R_λ

) of the considered pixel acquired at the same wavelength (λ

) and at different times and not affected by fires, clouds, veils, fog or the like;

considering several neighbouring days;

recognizing a clouds-free acquisition for each vector element as the one assuming the maximum spectral radiance value in the 10.8 or 12 μ

m wavelength band among those corresponding to the same vector element in the considered days; and

recognizing a fire-free acquisition for each clouds-free vector element already selected as the one assuming the minimum spectral radiance value in 3.9 μ

m wavelength band among those corresponding to the same vector element in the considered days

wherein computing, for each considered pixel, a temporal harmonic analysis includes;

forming a vector (h_λ

) containing the spectral radiances related to different times, and acquired at or predicted for the same wavelength (λ

); and

computing the temporal harmonic analysis of the vector (h_λ

).

8. A method for automatically detecting fires on Earth'"'"'s surface and atmospheric phenomena in Earth'"'"'s atmosphere by means of a satellite system, the method comprising:

acquiring multi-spectral images of the Earth at different times by means of a multi-spectral satellite sensor, each multi-spectral image being a collection of single-spectral images each associated with a respective wavelength (λ

), each single-spectral image being made up of pixels each indicative of a spectral radiance (R_λ

) from a respective area of the Earth;

computing an adaptive predictive model predicting spectral radiances (R_PRD,λ

) at a considered time for considered pixels on the basis of previously acquired spectral radiances (R_λ

) of the considered pixels and of spectral radiances (R_PRD,λ

) previously predicted for the considered pixels by said adaptive predictive model;

comparing acquired spectral radiances (R_λ

) of the considered pixels at a considered time with spectral radiances (R_PRD,λ

) predicted at the same considered time for the considered pixels by the adaptive predictive model; and

detecting a fire in areas of the Earth'"'"'s surface or an atmospheric phenomenon in areas of the Earth'"'"'s atmosphere corresponding to the considered pixels on the basis of an outcome of the comparison;

providing a physical model relating the spectral radiances (R_λ

) of the pixels in the multi-spectral images acquired at different times and physical quantities representing thermodynamic phenomena occurring on the Earth'"'"'s surface, including a possible fire on the Earth'"'"'s surface, in the Earth'"'"'s atmosphere, such as clouds, veils, fog or the like, and related to the Earth and the Sun relative positions; and

,

when, at a given time (t), no atmospheric phenomenon is detected in an area of the Earth'"'"'s atmosphere corresponding to a considered pixel, computing in the physical model, for the considered pixel, a background temperature (T_B,t) and a pixel fraction (f_t) representing an extension of a possible fire in an area of the Earth'"'"'s surface corresponding to the considered pixel on the basis of the spectral radiance (R<sub>λ

,t</sub>) of the considered pixel at the given time (t), of a previously acquired spectral radiance (R<sub>λ

,t-Δ

t</sub>) of the considered pixel, of a pixel fraction (f<sub>t-Δ

t</sub>) previously computed in the same physical model for the same considered pixel, and of the background temperature (T<sub>B,t-Δ

t</sub>) previously computed in the same physical model for the same considered pixel.

9. The method of claim 8, wherein providing a physical model comprises:

providing a dynamic multi-spectral equation system comprising at least one single-spectral equation associated with a respective wavelength (λ

), and relating the spectral radiances (R_λ

) of the considered pixels in single-spectral images acquired at different times to the physical quantities at the same times;

and wherein computing in the physical model, for the considered pixel, a background temperature (T_B,t) and a pixel fraction (f_t) comprises;

computing the pixel fraction (f_t) and the background temperature (T_B,t) by solving the dynamic multi-spectral equation system at the given time (t) for the considered pixel on the basis of the pixel fraction (f<sub>t-Δ

t</sub>) and the background temperature (T<sub>B,t-Δ

t</sub>) previously computed by having solved the dynamic multi-spectral equation system at a previous time (t-Δ

t) for the same considered pixel.

10. The method of claim 9, wherein the single-spectral equations in the dynamic multi-spectral equation system are based on differences between equations relating the spectral radiances (R_λ

) acquired at different times to the physical quantities at the same times.

11. The method according to claim 9, wherein the physical quantities in the physical model comprise at least one of the following quantities:

a fire temperature (T_F);

a Sun radiance (R_S,λ

);

a fire emissivity (ε

_F,λ

);

a background emissivity (ε

_B,λ

); and

an Earth'"'"'s atmosphere transmittance (τ

_λ

).

12. The method of claim 11, wherein the dynamic multi-spectral equation system is:

13. The method according to claim 8, further comprising:

detecting a fire in an area of Earth'"'"'s surface whether the pixel fraction (f_t) computed for the corresponding pixel satisfies a given criterion.

14. The method of claim 13, wherein detecting a fire in an area of the Earth'"'"'s surface whether the pixel fraction (f_t) computed for the corresponding pixel satisfies a given criterion includes:

filtering the pixel fraction (f_t) computed for a pixel by subtracting from the computed pixel fraction (f_t) a value correlated to a low-pass filtered sequence of previously computed pixel fractions (f<sub>t-Δ

t</sub>); and

detecting a fire in an area of the Earth'"'"'s surface whether the filtered pixel fraction () computed for the corresponding pixel is higher than a given threshold.