Abstract: In some embodiments, data from multiple vehicle-based natural gas leak detection survey runs are used by computer-implemented machine learning systems to generate a list of natural gas leaks ranked by hazard level. A risk model embodies training data having known hazard levels, and is used to classify newly-discovered leaks. Hazard levels may be expressed by continuous variables, and/or probabilities that a given leak fits within a predefined category of hazard (e.g. Grades 1-3). Each leak is represented by a cluster of leak indications (peaks) originating from a common leak source. Hazard-predictive features may include maximum, minimum, mean, and/or median CH4/amplitude of aggregated leak indications; estimated leak flow rate, determined from an average of leak indications in a cluster; likelihood of leak being natural gas based on other indicator data (e.g. ethane concentration); probability the leak was detected on a given pass; and estimated distance to leak source.

Abstract: An equal mixture of gas flows from multiple inputs is provided to gas analysis instrumentation, despite the unequal gas flow properties of the inputs often seen in practice. E.g., due to unequal input sample line lengths. We provide gas flow symmetry into a gas manifold that provides the output(s) to the gas analysis instrument(s). Such symmetry has two parts—equal gas flow properties from a set of reference points (one reference point for each input) to the manifold, and equal pressures at the reference points. Such equal pressures can be provided for unequal input gas flow properties by having a bypass valve for each input controlled so as to equalize the pressures.

Abstract: Improved optical absorption spectroscopy of species having broad spectral features is provided by choosing frequencies to cover the spectral feature(s) of interest, where the frequencies are slightly adjusted as needed to avoid narrow spectral features from interfering chemical species (i.e., clutter). The resulting clutter avoidance provides improved optical spectroscopy of species having broad spectral features.

Abstract: Improved gas leak detection from moving platforms is provided. Automatic horizontal spatial scale analysis can be performed in order to distinguish a leak from background levels of the measured gas. Source identification can be provided by using isotopic ratios and/or chemical tracers to distinguish gas leaks from other sources of the measured gas. Multi-point measurements combined with spatial analysis of the multi-point measurement results can provide leak source distance estimates. These methods can be practiced individually or in any combination.

Abstract: In some embodiments, data from multiple vehicle-based natural gas leak detection survey runs are used by computer-implemented machine learning systems to generate a list of natural gas leaks ranked by hazard level. A risk model embodies training data having known hazard levels, and is used to classify newly-discovered leaks. Hazard levels may be expressed by continuous variables, and/or probabilities that a given leak fits within a predefined category of hazard (e.g. Grades 1-3). Each leak is represented by a cluster of leak indications (peaks) originating from a common leak sources. Hazard-predictive features may include maximum, minimum, mean, and/or median CH4/amplitude of aggregated leak indications; estimated leak flow rate, determined from an average of leak indications in a cluster; likelihood of leak being natural gas based on other indicator data (e.g. ethane concentration); probability the leak was detected on a given pass; and estimated distance to leak source.

Abstract: Improved cavity enhanced absorption spectroscopy is provided using a piecewise tunable laser by using a lookup table for laser tuning that is configured specifically for this application. In preferred embodiments this is done in combination with a laser control strategy that provides precise wavelength determination using cavity modes of the instrument as a reference.

Abstract: Improved cavity enhanced absorption spectroscopy is provided using a piecewise tunable laser by using a lookup table for laser tuning that is configured specifically for this application. In preferred embodiments this is done in combination with a laser control strategy that provides precise wavelength determination using cavity modes of the instrument as a reference.

Abstract: Improved cavity enhanced absorption spectroscopy is provided using a piecewise tunable laser by using a lookup table for laser tuning that is configured specifically for this application. In preferred embodiments this is done in combination with a laser control strategy that provides precise wavelength determination using cavity modes of the instrument as a reference.

Abstract: Improved optical absorption spectroscopy of species having broad spectral features is provided by choosing frequencies to cover the spectral feature(s) of interest, where the frequencies are slightly adjusted as needed to avoid narrow spectral features from interfering chemical species (i.e., clutter). The resulting clutter avoidance provides improved optical spectroscopy of species having broad spectral features.

Abstract: Interleaved data acquisition in optical spectroscopy is used to provide interference correction for time-varying interference. Measurements at a reference frequency are used to provide an estimate of the interference. These reference measurements are interleaved with the remaining measurements in order to provide estimates of the interference vs. time at relevant times. The interference being corrected can be spectrally structured or unstructured.

Abstract: An equal mixture of gas flows from multiple inputs is provided to gas analysis instrumentation, despite the unequal gas flow properties of the inputs often seen in practice. E.g., due to unequal input sample line lengths. We provide gas flow symmetry into a gas manifold that provides the output(s) to the gas analysis instrument(s). Such symmetry has two parts—equal gas flow properties from a set of reference points (one reference point for each input) to the manifold, and equal pressures at the reference points. Such equal pressures can be provided for unequal input gas flow properties by having a bypass valve for each input controlled so as to equalize the pressures.

Abstract: In some embodiments, a natural gas leak detection system generates display content including indicators of remote and local potential leak source areas situated on a map of an area of a gas concentration measurement survey performed by a vehicle-borne device. The remote area may be shaped as a wedge extending upwind from an associated gas concentration measurement point. The local area graphically represents a potential local leak source area situated around the gas concentration measurement point, and having a boundary within a predetermined distance (e.g. 10 meters) of the gas concentration measurement point. The local area may be represented as a circle, ellipse, or other shape, and may include an area downwind from the measurement point. Size and/or shape parameters of the local area indicator may be determined according to survey vehicle speed and direction data, and/or wind speed and direction data characterizing the measurement point.

Abstract: In some embodiments, data from a vehicle-borne gas leak detection survey are used to generate an aggregate leak indication search area (LISA) indicator for a plurality of leak indications (measurement peaks) characterizing a single leak or localized set of leaks. A clustering algorithm (e.g. Markov, DBScan) may be used to group a set of indications into a cluster characterizing the leak. Leak indications may be pre-filtered for quality control before assignment to a cluster according to a number of parameters including background gas level, inter-peak distance, peak shape, wind speed, wind direction and/or variability, vehicle speed and/or acceleration, and/or a lower detection threshold for leak flow rate.

Abstract: A gas concentration image (i.e., concentration vs. position data) in a cross section through a gas plume is obtained. Such measurements can be obtained by using a 2D array of gas sample inlets, or by moving a 1D array of gas sample inlets through the gas plume. By combining a gas concentration image with ambient flow information through the surface of the gas concentration image, the leak rate (i.e., gas flux) from the leak source can be estimated. Gas samples are simultaneously acquired by filling two or more gas sample storage chambers. This is the default operation mode, which is convenient to regard as recording mode. The other operating mode is a playback mode, where the gas samples in the gas sample storage chamber are sequentially provided to a gas analysis instrument. Gas collection via line pixels can be used to compensate for vertical wind speed variation.

Abstract: Flux estimates for gas plumes from gas leaks are obtained from a 1-D horizontal line scan of gas concentration measurements, combined with an estimate of the vertical extent of the gas plume. In this manner, flux estimates for gas plumes can be obtained without having to gather a 2-D image of gas concentration data. In preferred embodiments, an estimate of the uncertainty of the gas plume flux estimate is provided.

Abstract: In some embodiments, a computer system generates display content indicating a likely direction and estimated distance to a potential gas leak source. The content includes a street map and at least one search area indicator on the map that indicates a search area suspected to have a gas leak source. The search area indicator has an axis indicating a representative wind direction relative to a geo-referenced location of at least one gas concentration measurement point. The search area indicator also has a width relative to the axis. The width is indicative of a wind direction variability associated with a plurality of wind direction measurements in an area of the gas concentration measurement point. The axis also preferably has a length indicating an estimated maximum distance to the potential gas leak source.

Abstract: Flux estimates for gas plumes from gas leaks are obtained from a 1-D horizontal line scan of gas concentration measurements, combined with an estimate of the vertical extent of the gas plume. In this manner, flux estimates for gas plumes can be obtained without having to gather a 2-D image of gas concentration data.

Abstract: In some embodiments, a natural gas leak detection system generates display content including indicators of remote and local potential leak source areas situated on a map of an area of a gas concentration measurement survey performed by a vehicle-borne device. The remote area may be shaped as a wedge extending upwind from an associated gas concentration measurement point. The local area graphically represents a potential local leak source area situated around the gas concentration measurement point, and having a boundary within a predetermined distance (e.g. 10 meters) of the gas concentration measurement point. The local area may be represented as a circle, ellipse, or other shape, and may include an area downwind from the measurement point. Size and/or shape parameters of the local area indicator may be determined according to survey vehicle speed and direction data, and/or wind speed and direction data characterizing the measurement point.

Abstract: In some embodiments, a natural gas leak detection system generates display content including indicators of remote and local potential leak source areas situated on a map of an area of a gas concentration measurement survey performed by a vehicle-borne device. The remote area may be shaped as a wedge extending upwind from an associated gas concentration measurement point. The local area graphically represents a potential local leak source area situated around the gas concentration measurement point, and having a boundary within a predetermined distance (e.g. 10 meters) of the gas concentration measurement point. The local area may be represented as a circle, ellipse, or other shape, and may include an area downwind from the measurement point. Size and/or shape parameters of the local area indicator may be determined according to survey vehicle speed and direction data, and/or wind speed and direction data characterizing the measurement point.

Abstract: Interleaved data acquisition in optical spectroscopy is used to provide interference correction for time-varying interference. Measurements at a reference frequency are used to provide an estimate of the interference. These reference measurements are interleaved with the remaining measurements in order to provide estimates of the interference vs. time at relevant times. The interference being corrected can be spectrally structured or unstructured.