Eye-safe lidar measurements for detection and investigation of forest-fire smoke (original) (raw)
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XVII International Symposium on Gas Flow, Chemical Lasers, and High-Power Lasers, 2008
The possibility of early forest fire detection within a range up to ~2 km using a portable eye-safe 1540 nm lidar is demonstrated in this paper, both on experimental and theoretical ground. An estimation of the detection efficiency using a mathematical model based on the 3D system of Navier-Stokes equations describing the smoke plume evolution in the presence of wind, agrees reasonably well with experimental results. Calculations made using the model show that a detection range up to ~5.5 km can be achieved by accumulating lidar return signals.
Feasibility of forest-fire smoke detection using lidar
International Journal of Wildland Fire, 2003
The feasibility and fundamentals of forest fire detection by smoke sensing with single-wavelength lidar are discussed with reference to results of 532-nm lidar measurements of smoke plumes from experimental forest fires in Portugal within the scope of the Gestosa 2001 project. The investigations included tracing smoke-plume evolution, estimating forest-fire alarm promptness, and smoke-plume location by azimuth rastering of the lidar optical axis. The possibility of locating a smoke plume whose source is out of line of sight and detection under extremely unfavourable visibility conditions was also demonstrated. The eye hazard problem is addressed and three possibilities of providing eye-safety conditions without loss of lidar sensitivity (namely, using a low energy-per-pulse and high repetition-rate laser, an expanded laser beam, or eye-safe radiation) are discussed.
Fire Surveillance and Evaluation by Means of Lidar Technique
Lidar (light detection and ranging) is an active remote detection technique that uses a pulsed laser beam to probe the atmosphere. When the laser radiation illuminates a target, such as a smoke plume originating from a forest fire, part of the incident radiation is backscattered, the intensity of this radiation is measured as a function of time by a suitable detector, and the resulting signal is analyzed by artificial intelligence methods. If the signature of a smoke plume is identified, an alarm is emitted. Precise position of the smoke plume is derived from the current azimuth/elevation angles of the laser beam (provided by the scanning system) and the distance to the target (calculated from the detection time).
Simple eye-safe lidar for cloud height measurement and small forest fire detection
Optics and Spectroscopy, 2010
A simple and robust eye-safe lidar was developed on the basis of a rangefinder optical scheme comprising an Er:glass laser which generates 8 mJ pulses of 1540-nm radiation with the pulse repetition rate of 0.17 Hz and a 38-mm-diameter telescope. Reliable measurements of the cloud height up to 3700 m and early forest-fire detection with a range of 3000 m were experimentally demonstrated. Theoretical estimations indicate that using an optical scheme built around a 10 Hz Er:glass lasers and 150 mm light gathering optics early forest fire detection in a range up to 6500 m can be achieved.
Comparison of eye-safe UV and IR lidar for small forest-fire detection
Remote Sensing for Agriculture, Ecosystems, and Hydrology III, 2002
Lidar is a promising tool for forest-fire monitoring because this active detection technique allows efficient location of tenuous smoke plumes resulting from forest fires at their early stages. For the technique to be generally usable, instrumentation must be eye-safe, i. e. it must operate within the spectral range λ<0.4 or λ>1.4 µm. In this paper the lidar efficiency at the wavelengths 0.3472 µm (second harmonic of the ruby laser) and 1.54 µm (Er:glass laser) are compared using a theoretical model. The results of calculations show that the energy required for smoke-plume detection using 0.3472 µm becomes greater than the corresponding value for 1.54 µm when the distance exceeds some threshold, which ranges between 2 and 6 km depending on other parameters. Being caused by relatively higher absorption of the UV radiation in the atmosphere, this result is valid for any wavelength in the vicinity of 0.35 µm, for example, the third harmonic of Nd:YAG laser and the second harmonic of Ti:sapphire laser.
Application of lidar in ultraviolet, visible and infrared ranges for early forest fire detection
Applied Physics B: Lasers and Optics, 2003
The efficiency of directs lidar operating at 355, 532, 1064, and 1540 nm radiation wavelengths for early forest-fire detection was compared. For each wavelength the range for reliable smoke plume detection was estimated on the basis of computer simulation plume using a one-dimensional "top hat" gas dynamic model for the calculation of the backscattering and extinction coefficient profiles within the plume. The agreement between the predicted signal-to-noise ratio (SNR) and experimental results for 532 and 1064 nm wavelength radiation is good. The decrease of the signalto-noise ratio with distance is maximum for 355 nm and minimum for 1064 nm. At 1540 nm the decay of SNR with distance is slightly faster, but the SNR is higher than for other wavelengths, leading to the highest detection efficiency for the same energy of the probing laser pulse. For a burning rate of 2 kg/s and a laser beam divergence of 2.5 mr, the maximum distance for reliable detection varies between 6 and 12 km, depending on the wavelength.
Application of lidar at 1.54 um for forest fire detection
1999
A mathematical model for computation of parameters of eyesafe lidar for detection of forest fire smoke has been developed. It is assumed that the lidar uses a wavelength of 1.54 micrometer. This wavelength can be obtained from Er:glass lasers, from Nd:YAG lasers with an optical parametric oscillator, or from Nd:YAG lasers with a Raman cell. It is assumed that receiver optics of 20 cm diameter and an avalanche photodiode are used. Particle size distributions in the smoke from experiments in the literature are utilized for calculation of backscattering efficiency. The backscattering cross section is calculated on the basis of Mie formulae. Diffusion of the smoke plume is estimated on the basis of an analytical solution of the relevant hydrodynamics equations. Results of the calculations show that for detection of forest fires with fuel mass burned in unit time 2 kg/s at a distance of 10 km it is necessary to have a laser pulse energy of 120 mJ.
Application of lidar at 1.54 μm for forest fire detection
Remote Sensing for Earth Science, Ocean, and Sea Ice Applications, 1999
A mathematical model for computation of parameters of eyesafe lidar for detection of forest fire smoke has been developed. It is assumed that the lidar uses a wavelength of 1.54 m. This wavelength can be obtained from Er:glass lasers, from Nd:YAG lasers with an optical parametric oscillator, or from Nd:YAG lasers with a Raman cell. It is assumed that receiver optics of 20cm diameter and an avalanche photodiode are used. Particle size distributions in the smoke from experiments in the literature are utilised for calculation of backscattering efficiency. The backscattering cross section is calculated on the basis of Mie formulae. Diffusion of the smoke plume is estimated on the basis of an analytical solution of the relevant hydrodynamics equations. Results of the calculations show that for detection of forest fires with fuel mass burned in unit time 2 kg/s at a distance of 10 km it is necessary to have a laser pulse energy of 120 mJ.
Estimation of required parameters for detection of small smoke plumes by lidar at 1.54��m
Appl Phys B Lasers Opt, 2000
Parameters of eyesafe lidar at 1.54 µm for detection of small plumes of smoke from burning wood or oil have been evaluated. It was assumed that a diode-pumped solid-state Er:glass laser at 1.54 µm or a Nd:YAG laser with a Raman cell or optical-parametric oscillator is used as a light source and that detection of backscattered light is performed with an avalanche photodiode. Ash and soot particle size distributions were taken from experiments. A backscattering coefficient at 1.54 µm for various source of smoke was estimated. In computing the laser energy, range between lidar and smoke, receiver optics diameter, fuel mass burned in unit time, fire source radius, laser pulse duration and visibility were varied. Results of the computations enabled estimation of the required laser energy, which ranges from 0.05 to 1400 mJ depending on the parameters. PACS: 42.68.Wt; 92.60.Mt Detection of smoke from sources such as power plants, factories, forest fires, etc., was one of the first practical applications of lidar . Smoke contains a large number of small particles of ash or soot, leading to a large backscattering efficiency and consequently favourable conditions for lidar application. The use of lidar increased considerably during the following years, and this technology is now widely used . In general the first lidars used ruby or Nd:YAG lasers (wavelength 694 and 1064 nm, respectively), which are dangerous to the eye. They were applied to the investigation of plumes, which have a great output of smoke. However the modern tendency in lidar is to use lasers with eyesafe wavelengths (at 1.54 or ≈ 2.1 µm [5, 6]) and to increase its sensitivity, allowing increasingly small sources of smoke to be detected . It is obvious that detection of the early stages of a fire, when smoke plumes are tenuous, allows the means required to extinguish the fire and fire damage to be minimized. For eyesafety, lidars with a wavelength within the range ≈ 1.54 µm are increasingly being used. It is possible in this lidar to use solid-state Er:glass lasers at 1.54 µm, Nd:YAG lasers with a Raman cell at 1.54 µm [9], and Nd:YAG lasers with opticalparametric oscillators (OPO) . Detection of smoke is pos-sible by direct or heterodyne detection mode . But it is known [5] that OPO leads to frequency instability, so in this case it is preferable to use lidar with direct-detection mode.
Estimation of required parameters for detection of small smoke plumes by lidar at 1.54 μm
Applied Physics B, 2000
Parameters of eyesafe lidar at 1.54 µm for detection of small plumes of smoke from burning wood or oil have been evaluated. It was assumed that a diode-pumped solid-state Er:glass laser at 1.54 µm or a Nd:YAG laser with a Raman cell or optical-parametric oscillator is used as a light source and that detection of backscattered light is performed with an avalanche photodiode. Ash and soot particle size distributions were taken from experiments. A backscattering coefficient at 1.54 µm for various source of smoke was estimated. In computing the laser energy, range between lidar and smoke, receiver optics diameter, fuel mass burned in unit time, fire source radius, laser pulse duration and visibility were varied. Results of the computations enabled estimation of the required laser energy, which ranges from 0.05 to 1400 mJ depending on the parameters. PACS: 42.68.Wt; 92.60.Mt Detection of smoke from sources such as power plants, factories, forest fires, etc., was one of the first practical applications of lidar . Smoke contains a large number of small particles of ash or soot, leading to a large backscattering efficiency and consequently favourable conditions for lidar application. The use of lidar increased considerably during the following years, and this technology is now widely used . In general the first lidars used ruby or Nd:YAG lasers (wavelength 694 and 1064 nm, respectively), which are dangerous to the eye. They were applied to the investigation of plumes, which have a great output of smoke. However the modern tendency in lidar is to use lasers with eyesafe wavelengths (at 1.54 or ≈ 2.1 µm [5, 6]) and to increase its sensitivity, allowing increasingly small sources of smoke to be detected . It is obvious that detection of the early stages of a fire, when smoke plumes are tenuous, allows the means required to extinguish the fire and fire damage to be minimized. For eyesafety, lidars with a wavelength within the range ≈ 1.54 µm are increasingly being used. It is possible in this lidar to use solid-state Er:glass lasers at 1.54 µm, Nd:YAG lasers with a Raman cell at 1.54 µm [9], and Nd:YAG lasers with opticalparametric oscillators (OPO) . Detection of smoke is pos-sible by direct or heterodyne detection mode . But it is known [5] that OPO leads to frequency instability, so in this case it is preferable to use lidar with direct-detection mode.